Chapter VI – PAVEMENT EVALUATION AND · PDF filesection 601 – fundamental concepts...

January 2018

SECTION 601 – FUNDAMENTAL CONCEPTS OF PAVEMENT DESIGN AND EVALUATION................................................................................................................... 3

Sec. 601.01 Introduction ................................................................................................. 3

Sec. 601.02 Project Pavement Evaluations ..................................................................... 4

Sec. 601.03 Patching Survey Guidelines ...................................................................... 17

SECTION 602 – FALLING WEIGHT DEFLECTOMETER TESTING AND ANALYSIS GUIDELINES ................................................................................................................... 22

Sec. 602.01 Introduction ............................................................................................... 22

Sec. 602.02 FWD Testing ............................................................................................. 22

Sec. 602.03 FWD Data Processing ............................................................................... 22

SECTION 603 – GUIDELINES FOR USE OF THE MECHANISTIC-EMPIRICAL PAVEMENT DESIGN ..................................................................................................... 25

Sec. 603.01 Purpose ...................................................................................................... 25

Sec. 603.02 Pavement Design ....................................................................................... 25

SECTION 604 – GUIDELINES FOR USE OF THE 1993 AASHTO PAVEMENT DESIGN PROCEDURE ................................................................................................... 28

Sec. 604.01 Purpose ...................................................................................................... 28

Sec. 604.02 Flexible Pavement Design ........................................................................ 28

Sec. 604.03 Rigid Pavement Design ............................................................................. 35

SECTION 605 – ASPHALT CONCRETE MIX SELECTION GUIDELINES .............. 43

Sec. 605.01 Purpose Of Guidelines .............................................................................. 43

Sec. 605.02 Description Of Asphalt Concrete Mixes ................................................... 43

Sec. 605.03 VDOT Asphalt Binders ............................................................................. 48

Sec. 605.04 Asphalt Mix selection – General Applications ......................................... 49

Sec. 605.05 Asphalt Binder and Mix selection – Specialized locations ....................... 52

Sec. 605.06 Application Rates ...................................................................................... 53

Sec. 605.07 Typical asphalt Base mix application rates ............................................... 54

SECTION 606 – PAVEMENT TYPE SELECTION PROCEDURES DETAILS ......... 56


Sec. 606.02 Pavement Type Selection .......................................................................... 56

Sec. 606.03 Pavement Types ........................................................................................ 56

Sec. 606.04 Pavement Design ....................................................................................... 57

Sec. 606.05 Pavement Type Selection Procedures (PTSP) .......................................... 57

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Sec. 606.06 Alternate Bidding ...................................................................................... 60

Sec. 606.07 How To Use The Procedures .................................................................... 60

SECTION 607 – LIFE CYCLE COST ANALYSIS ....................................................... 63

Sec. 607.01 Executive Summary .................................................................................. 63


Sec. 607.03 Economic Analysis Components .............................................................. 65

Sec. 607.04 Cost Factors ............................................................................................... 67

Sec. 607.05 Overview Of LCCA Pavement Options .................................................... 69

Sec. 607.06 Asphalt Pavement Construction/Reconstruction ...................................... 70

Sec. 607.07 Jointed Concrete Pavement Construction/Reconstruction With Tied Portland Cement Concrete Shoulders ....................................................... 74

Sec. 607.08 Jointed Plain Concrete Pavement Construction/Reconstruction With Wide Lane (14 Feet) And Asphalt Concrete Shoulders ..................................... 77

Sec. 607.09 Continuously Reinforced Concrete Pavement Construction/Reconstruction With Tied Portland Cement Concrete Shoulders ...................................... 79

Sec. 607.10 Continuously Reinforced Concrete Pavement Construction/Reconstruction With Wide Lanes (14 Feet) And AC Shoulders ....................................... 81

Sec. 607.11 LCCA For Major Rehabilitation Projects ................................................. 83

Sec. 607.12 Unit Costs And Measures ......................................................................... 83

Sec. 607.13 Interpretation Of Results ........................................................................... 84

SECTION 608 – PROJECT SELECTION GUIDELINES FOR COLD PAVEMENT RECYCLING ............................................................................................ 85

Sec. 608.01 Purposes and Goal ..................................................................................... 85

Sec. 608.02 Definitions ................................................................................................. 86

Sec. 608.03 Selection of Rehabilitation/Construction Projects .................................... 86

Sec. 608.04 Exceptions ................................................................................................. 90

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Chapter VI – PAVEMENT EVALUATION AND DESIGN

SECTION 601 – FUNDAMENTAL CONCEPTS OF PAVEMENT DESIGN AND EVALUATION

SEC. 601.01 INTRODUCTION

One of the State of Virginia’s largest assets, if not the largest asset, is the highway network system. The Virginia Department of Transportation (VDOT) is responsible for maintaining the third largest roadway network in the United States encompassing over 53,000 miles. VDOT’s Materials Division’s Pavement Design and Evaluation (PD&E) Section is responsible for the review and comment on new and rehabilitated pavement structures around the state. PD&E assists the districts in the overall management of Virginia’s highway construction program by providing guidance, technical assistance and training.

An important function in pavement management is project level analysis of existing roadway sections. Project level analysis is the inspection of existing pavements to determine the causes of deterioration and to assess the current condition. Once project level analysis has been conducted, then the most reliable pavement design can be performed. For new construction and rehabilitation projects, the combining of existing condition data, future traffic projections, soil subgrade properties and paving material properties will ensure a proper pavement design. This analysis and design should apply not only to pavement reconstruction and rehabilitation projects, but to routine and preventative maintenance projects as well.

The purpose of this document is to provide guidelines for VDOT’s Pavement designers in conducting project evaluations and pavement designs on Major (Interstate, Primary, Urban and High-Volume Secondary) Roadways and Minor (Low-Volume Secondary and Sub-Division) Roadways. The amount of pavement evaluation required will be dependent on the scope of the project; the pavement design process will depend on the roadway classification (Interstate, Primary or Secondary). This document covers design considerations for routine maintenance, rehabilitation and construction activities performed by VDOT. However, it does not preclude from consideration of new and innovative pavement techniques.

NOTE: The requirements for pavement design, as established herein, shall be followed unless waived by the District Materials Engineer or District Materials Engineer designee.

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SEC. 601.02 PROJECT PAVEMENT EVALUATIONS

Major Roadway project evaluation process is a two-step procedure: Step 1 – Preliminary Pavement Analysis and Design, Step 2 – Detailed Pavement Evaluation and Design. Major Roadways consist of Interstate, Major and Minor Arterial, and Major and Minor Collector routes. Step 1 occurs during the project-scoping phase. Step 2 occurs after the scoping phase during the Planning, Specifications and Estimating (detailed design) development.

The details for these evaluations are provided in the following sections.

(a) Preliminary Pavement Evaluation

Step 1 is the preliminary pavement analysis and design. This process will occur once the District Materials Engineer has been notified that a project requires a pavement design. Ideally, the Location and Design Section will notify the District Materials Engineer prior to establishing a preliminary construction estimate. With pavement items being a large percentage of the overall construction cost, a good initial estimate will aid L&D in requesting construction funds. At the preliminary evaluation and design phase of a project, the PD&E Section may provide technical assistance to the Pavement designer upon request. To conduct the preliminary pavement evaluation, the Pavement designer will conduct 4 tasks. These tasks are:

Task 1. Data Gathering

Task 2. Field Data Collection

Task 3. Preliminary Recommendation

Task 4. Determine Need for Detailed Pavement Evaluation

Figure 1 shows the process flow for the preliminary pavement evaluations.

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Figure 1 - Preliminary Pavement Evaluation Process Flow

Task 1. Data Gathering:

Traffic Data

Pavement Layer Data

Soil Data

Visual Condition (if relevant)

Ride Quality (if relevant)

Friction Data (if relevant)

Maintenance Data (if relevant)

Structural Capacity

Task 2. Field Data Collection

Patching Estimate Survey

Task 3. Perform Preliminary Pavement Evaluation

Task 4. Determine Need for Detailed Pavement Evaluation

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Task 1. Data Gathering For construction projects where existing pavement is to be utilized, data will be gathered prior to performing a preliminary evaluation. If available and relevant to the project, the Pavement designer will gather: • Traffic Data (AADT, ESAL Factor, % Trucks, etc.),

• Pavement Layer Data (Materials, Thickness’, Year Constructed)

• Soil Condition Data (Type and Strength),

• Visual Condition Data,

• Ride Quality Data,

• Structural Capacity Data,

• Friction Data, and

• Maintenance Data (including dates and types of rehabilitation).

Much of this pavement data may be contained in Maintenance Division’s Pavement Management System (PMS); however, the data must be validated prior to conducting the analysis. It is important to remember that for projects that include the widening of an existing pavement, realignment of a roadway (where a portion of the existing pavement is used), or other projects where the existing pavement is part of the final design, the existing pavement must be evaluated and addressed in the final pavement recommendation.

Task 2. Patching Estimate Survey For a preliminary evaluation, minimal field data collection is required. The Pavement designer will perform a limited visual survey on the pavement surface and drainage structures (i.e. curb and gutter, ditches, underdrains), unless waived by the District Materials Engineer.

Where the existing pavement is to be utilized, proper patching of deteriorated pavement is necessary at the time of maintenance/rehabilitation. The Pavement designer will estimate the amount of full-depth and partial depth patching required by performing a survey, unless waived by the District Materials Engineer. Approximate areas of pavement experiencing alligator cracking, rutting and localized failures should be used to estimate patching types and quantities. Refer to SECTION 601.03 for guidance in determining patching type based on distresses observed.

Note: • Full-Depth Patches are defined as removing all Portland Cement Concrete (PCC) / AC material

– surface mix, intermediate mix and base mix by milling, carbide grinding or saw cutting, but not the granular or stabilized base/sub-base unless determined necessary by the field engineer.

• Partial Depth Patches are defined as removing a portion of the total PCC/AC thickness by milling or carbide grinding.

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In addition, the Pavement designer will consider the pavement drainage conditions and their effects on the current pavement condition and potential rehabilitation alternatives. This will include, but not be limited to: • Curb and gutter condition;

• Curb reveal;

• Shoulders;

• Side ditches;

• Underdrains; and

• Medians.

•

Finally, the Pavement designer should note any other pertinent information related to the project that may affect the final pavement design. Examples are poor roadway geometry (excessive cross-slope, excessive crown, etc.), guardrail height, bridge clearances, etc. While the Pavement designer is not responsible for measuring or assessing these items, general knowledge of these items will assist in developing pavement options.

Task 3. Preliminary Recommendation Upon completion of the field data collection and data analysis, the Pavement designer will develop a preliminary pavement recommendation.

Subtask 3.1. Data Analysis For each project, a minimal amount of data analysis should be required. The Pavement designer will:

Calculate the cumulative number of ESALS (if necessary) based on available traffic data;

For Mechanistic-Empirical Pavement Design (MEPDG), obtain the average annual daily truck traffic (AADTT) and if available, tuck distribution;

For new construction and reconstruction, determine the required pavement section needed following the procedure given in Section 603:

Calculate the required structural capacity for rehabilitation/overlay design using the procedures given in SECTION 604;

This analysis should be conducted to ensure a good initial construction estimate as well as to inform the Location and Design Section of possible pavement requirements for the project.

Subtask 3.2. Preliminary Pavement Report Once the data analysis is completed, the Pavement designer will prepare a preliminary pavement report. This report will document the project’s description, existing pavement structure, traffic levels, surface condition, and recommended improvement or improvement options.

Based on the recommended improvement or improvement options, a cost estimate can be developed by the project manager. If several improvement options are available and the

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project meets the life cycle cost analysis (LCCA) requirements outlined in SECTION 607.02, then a LCCA should be performed.

Task 4. Determine Need for Detailed Pavement Evaluation (Non-Construction Program Projects) Once the preliminary pavement evaluation is complete, the Pavement designer must determine if the project requires a Detailed Pavement Evaluation. This task applies to projects not in the Six-Year Improvement Program (SYIP). Projects in the SYIP will be subject to a detailed pavement evaluation.

For routine maintenance activities a detailed project level analysis will not be required. These activities include: • Crack Sealing;

• AC Overlay (1.5” or less) based on AASHTO Pavement Design (no additional structure is required, overlay required to improve ride or friction characteristics only);

• AC Overlay (2.0”) based on AASHTO Pavement Design (less than 5% of the pavement surface requires patching);

• Surface Treatment (less than 5% of the pavement surface requires patching); and

• Patching (less than 5% of the pavement surface requires patching).

For those projects that require more than 5% patching or require a structural capacity improvement based on the preliminary data analysis conducted in Subtask 3.1, then a Detailed Pavement Evaluation will be conducted.

(b) Detailed Pavement Evaluation

The detailed pavement evaluation will serve several purposes. First, the evaluation will refine the preliminary pavement recommendation. Second, the Pavement designer will be able to provide a better construction estimate to aid in allocating funds within the district. And third, the final pavement recommendation will aid the highway designer in developing construction documents (plans, specifications, etc.). This evaluation will help ensure proper improvements and designs to VDOT’s assets.

To conduct a detailed pavement evaluation, the following tasks will be performed: Task 1. Records Review

Task 2. Traffic Data Analysis

Task 3. Pavement Data Collection and Analysis

Task 4. Maintenance and Rehabilitation Pavement Design/New Design

Task 5. Final Report

Task 6. Project File Submittal to Pavement Design and Evaluation Section

Figure 2 shows the process flow for the detailed pavement evaluations.

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Figure 2 - Detailed Pavement Evaluation Process Flow

Task 1. Records Review As performed in the preliminary evaluation, the Pavement designer will conduct a record review to update and expand the data previously gathered. This review will concentrate on construction history, maintenance history, and pavement performance data (current and historical). For new construction projects, Task 1 can be omitted.

By reviewing “As-Built” construction plans and pavement history information in PMS (if available), the following data should be collected:

• Years of Construction (original and resurfacing),

• Pavement Ride Quality (if relevant),

• Pavement Surface Friction (if relevant),

• Pavement Layer Materials, and

• Subgrade Soil Types and Strengths.

• Pavement Performance History (LDR, NDT, CCI), if available.

Gather Project Records

Years of Construction

Ride and Friction Data (if relevant)

Pavement Layer Data

Subgrade Soils

Pavement performance Data

Conduct Traffic Data Analysis AADT (AADTT)

Trucks by Classification

ESAL Factor (if necessary)

Pavement Data Collection and Analysis FWD Testing

GPR Testing

Preliminary Structural Data Analysis

Coring and Boring

Pavement Design

Maintenance Activities

Functional and Structural Overlays

New Construction Final Project Report with Recommendations

Final Project File Submittal to PD&E for Review

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With use of the PMS, the Pavement designer should be able to obtain current and historical pavement performance data, which will be beneficial in Task 4.

Task 2. Traffic Data Analysis Unlike the preliminary pavement evaluation, a more detailed traffic data analysis is required. For the preliminary evaluation, the Pavement designer will gather available traffic data from the PMS and/or possibly District Traffic Engineering or Transportation Planning Sections. This data may only consist of average daily traffic counts, but may not contain information on the number and types of trucks using the roadway. For the detailed evaluation, more accurate data may be required depending on the information used for the preliminary evaluation and the preliminary pavement recommendation.

Traffic data to be collected should include: • Average Annual Daily Traffic

• Average Annual Daily Truck Traffic (MEPDG)

• Number of Trucks by Classification

• ESAL Factor by Classification

• Traffic Growth Rate

• Truck Weights (if available from weigh station)

In the event some or all of this information is not available, the Pavement designer will request the Traffic Engineering Section to conduct at least a 12 hour traffic study and to provide an estimate of the daily (24-hour) traffic. At a minimum, this study should provide an estimate of the AADT, percent trucks, and classification of trucks using the roadway.

Once traffic data are collected, the Pavement designer will conduct a traffic analysis for the pavement design period. The purpose of this analysis will be to determine the required structural capacity for the pavement based on the expected/forecast traffic loading (cumulative ESALS). If the pavement requires an overlay, the Pavement designer can use the remaining life method as outlined in the 1993 AASHTO Guide for Design of Pavement Structures.

Task 3. Pavement Data Collection and Analysis Under Task 3, the Pavement designer will perform the following data collection and analysis activities:

Subtask 3.1. Falling Weight Deflectometer (FWD) Testing

Subtask 3.2. Preliminary Structural Data Analysis

Subtask 3.3. Pavement Coring and Subgrade Boring

Subtask 3.4. Final Pavement Structural Analysis

Subtask 3.5. Patching Survey

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Subtask 3.1. Falling Weight Deflectometer and Ground Penetrating Radar (GPR) Testing The purpose of FWD testing (Figure 3) is to assess the existing structural condition of the pavement and strength of the subgrade soils. FWD testing can be conducted on flexible, rigid and composite pavements. The amount and specifics of the testing for each type of pavement is contained in SECTION 602 of this document. The purpose of GPR testing is to determine the consistency of the pavement thickness throughout the section. This testing can be performed in conjunction with FWD testing or separately. Collection of GPR data can aid a Pavement designer in evaluating FWD data in Modtag. To provide further clarification for consistency of pavement thickness, it is recommended that the thicknesses of the pavement cores taken be used to define the homogeneous sections within the project limits.

Figure 3 - Falling Weight Deflectometer

Subtask 3.2. Preliminary Structural Data Analysis Upon completion of FWD and/or GPR testing, the Pavement designer will perform a section analysis of the data. This may be done by using the cumulative sums of deflection method outlined in Appendix J of the 1993 AASHTO Guide for the Design of Pavement Structures. The Pavement designer will determine homogeneous sections of pavement and subgrade strength based upon deflection response as depicted in Figure 4. These homogeneous sections will be identified for pavement coring and possibly subgrade boring to determine the actual pavement structure. In addition, these sections will be used as analysis units in Task 4. A more detailed description of this process is contained in SECTION 602.

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-1.5

-1

-0.5

0

0.5

1

Cumulative Sum

Distance (feet)

Cumulative Sum vs. Deflection

Figure 4 - Example of Cumulative Sums Deflection

Subtask 3.3. Pavement Coring and Subgrade Boring Once pavement coring and boring locations has been identified in Subtask 3.2, the Pavement designer will arrange the coring and boring operations. For pavement coring, at a minimum, the following should be recorded:

• Pavement Material Types

• Thickness and

• Visual Condition

For the subgrade borings, at a minimum, a visual classification of the materials, moisture contents of the material, depth to water table, blow counts and retrieval of a bulk sample should be conducted. For resilient modulus testing, unconfined compressive strength and laboratory classification, adequate volume of material shall be recovered from the borings. For investigating existing pavements, the depth of borings shall be 5 feet unless otherwise directed by the Pavement designer. . Please refer to Chapter III of the Manual of Instructions for more information on coring, boring and laboratory testing.

Homogeneous Section 1

Homogeneous Section 2 Homogeneous Section 3

Homogeneous Section 4

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Subtask 3.4. Final Pavement Structural Analysis Once the exact pavement structure and subgrade is known, the Pavement designer will conduct a final pavement structural analysis using the FWD data collected in Subtask 3.1. Please refer to SECTION 602 for guidance on structural analysis using FWD data. This analysis will be used to determine the existing structural capacity of the pavement. For flexible pavements, the Pavement designer will determine: • Effective Structural Number (SNeff)

• Layer Moduli and

• Resilient Modulus of the Subgrade.

Figure 5 – Deflection Basin Collected with Falling Weight Deflectometer

For rigid pavements, the Pavement designer will determine: • Elastic Modulus of the PCC

• Composite Modulus of Subgrade Reaction

• Load Transfer at Cracks and Joints and

• Potential for the Presence of Voids.

For composite pavements, the Pavement designer will determine: • Elastic Modulus of the PCC

• Composite Modulus of Subgrade Reaction

• Resilient Modulus of the Subgrade.

• Load Transfer of Cracks and Joints and

• Potential for the Presence of Voids.

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These results will be used to design the future improvement of the roadway. SECTION 604 contains guidelines and recommendations for pavement analysis and designs.

Subtask 3.5. Patching Survey For projects where the existing pavement will be incorporated into the final pavement design, the Pavement designer will determine the amount of full-depth and partial depth patching required. The Pavement designer should consider the time that will elapse between investigation and construction and whether any potential deterioration of the pavement could increase the amount of patching. For projects where the existing pavement will be demolished, this subtask can be omitted.

The amount of patching will be based on guidelines provided in SECTION 601.03 and the engineer’s judgment. Please remember, if the total AC thickness is 8 inches and the final pavement recommendation calls for removing and replacing 2”, then partial depth patches may not be required. Note: • Full-Depth Patches are defined as removing all PCC/AC material – surface, intermediate and

base mixes, etc., by milling, carbide grinding or saw cutting, but not the granular or stabilized base/sub-base unless determined necessary by the field engineer.

• Partial Depth Patches are defined as removing a portion of the total PCC/AC thickness by milling or carbide grinding.

Guidelines for determining patch locations and types for PCC and AC surfaces are contained in SECTION 601.03.

Task 4. Pavement Design Upon completion of Task 3, the Pavement designer will develop a pavement design for the project. In general, a project will require one or more of the following: • Maintenance Activities

• Functional Overlay

• Structural Overlay

• Full-depth Base Widening

• Reconstruction/New Construction

Maintenance Activities For projects requiring a maintenance improvement, the Pavement designer will specify the maintenance to be performed. Maintenance activities may include, but not be limited to: • Partial Depth Patches,

• Full Depth Patches,

• Crack Sealing,

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• Surface Treatment (Slurry Seal, Micro surfacing, Chip Seal, etc.),

• Joint Sealing,

• Joint Cleaning, and

• Slab Stabilization.

The maintenance activity(s) designed should be based upon some of the following roadway attributes: • Pavement Distress,

• Pavement Type,

• Maintenance Activity Performance

• Traffic Level and

• District Preferences (chip seal vs. slurry seal).

It will be the responsibility of the Pavement designer to investigate these attributes.

Functional and Structural Overlays For projects requiring a functional or structural improvement, the Pavement designer will perform pavement designs as well as specify any maintenance to be performed. The pavement designs are to be based on current AASHTO procedures. The Pavement designer will use data collected in Task 3 to determine the current pavement condition and future requirements based on anticipated traffic. Where possible the Pavement designer will develop multiple alternatives for a project in order to perform life cycle cost comparisons. If the existing pavement may be removed, then the Pavement designer will refer to Section 606 on Pavement Type Selection. If the pavement is to remain in place, the Pavement designer will consider changing maintenance approaches (more vs. less patching), changing overlay thickness, changing milling thickness, changing materials, etc. For rigid pavements, concrete pavement restoration (CPR) may include joint/crack patching, grinding, dowel bar retrofit, etc. When CPR is considered by the Pavement designer , a 10-year design life will be used. The specifics on pavement design are contained in SECTION 604; the specifics on life cycle cost analysis are contained in Section 607.

Task 5. Final Report For each project, the Pavement designer will prepare a final report to document the technical approach and recommendations. This report will contain the following:

Section 1 - Specific Location of the Project

Section 2 - Existing Pavement Information (Rehab and Widening/Capacity Improvement Projects)

Subsection 2.1 - Pavement Structure

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Subsection 2.2 - Pavement Condition based on Ride Data (IRI), Structural Capacity (FWD Testing Results), and Visual Condition (Distress Survey)

Section 3 - Soils Information based on Soils Report - Unsuitable Materials, Select Material, etc.

Subsection 3.1 - Unsuitable Materials at Subgrade

Subsection 3.2 - Unsuitable Materials in Cut Areas

Subsection 3.3 - Shrinkage Factors for Excavation

Subsection 3.4 - Slope Design

Subsection 3.5 – Rock at Subgrade and in Cut Areas

Section 4 – Traffic Analysis Summary

Subsection 4.1 – General Information (AADT for Design Year, AADTT for Design Year, Growth Rate, Truck Percentage, Truck Classes, ESAL Factor)

Subsection 4.2 – Cumulative ESAL Computations if necessary

Section 5 – Pavement Recommendations

Subsection 5.1 – Mainline Roadway

General Description of Pavement Design

Parameters/Assumptions used in Pavement Design (Mr, CBR, Unconfined Compressive Strength of Soil, Design Life, Reliability, etc.)

Description of Patching (Quantity required, locations, quantity to remove, Patching Material and Specifications)

Description of Pavement Design Cross Section with Notes

Drainage Considerations (subsurface drainage – see Section 603 for MEPDG and Section 604 for AASHTO 1993)

Shoulder Design Details (see Section 603 for MEPDG and Section 604 for AASHTO 1993)

Subsection 5.2 – Connecting Roadways, Ramps, etc. (same as outlined above)

Section 6 – Sources of Material

Not all report sections will be required for all projects. It is the responsibility of the Pavement designer to determine what sections are to be included in the final report. Much of this information will be contained in separate appendices attached to the report. This information may include:

Detailed Structural and Functional Condition Data (Section 2) Detailed Soils Information (Section 3) Detailed Traffic Analysis (Section 4) Pavement Design Parameters (Section 5)

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Section 3 is not intended to replace the Soils Report, but summarize the information for the project designer(s).

The final recommendation will provide details on the materials to be used, material thickness, maintenance, etc. If necessary, the Pavement designer will provide any special provisions for construction and pavement cross sections. The main purpose of this report is to aid District Location and Design personnel in preparing project plans and contract documents.

Task 6. Project File Submittal to PD&E for Review and Comment Once the Pavement designer has obtained approval from the District Materials Engineer, the project file may be submitted to the Materials Division’s Pavement Design and Evaluation Section for review and comment in accordance with Section 606.07. Projects that are not required by Section 606.07 to be submitted for review, the District can opt to submit those projects to Pavement Design and Evaluation Section for review. However, all project files shall be submitted to Pavement Design and Evaluation for tracking purposes.

Whether or not a project report is submitted to PD&E for review, all Districts should use the following Pavement Recommendation Project File Format for their own review. This format will aid PD&E in the review of the projects by providing the right information at the right time. Additionally, this will provide complete design information for projects when it is needed for future reference. At a minimum, the file will contain:

• Cover Memo

• Pavement Design/Rehabilitation Report with Appendices

• General Pavement Details

• Pavement Design Software input and output values

• Traffic Analysis

• Existing Pavement Condition Surveys (Applies to Rehab Projects and Widening/Capacity Improvement Projects)

SEC. 601.03 PATCHING SURVEY GUIDELINES

The Pavement designer should estimate the amount of patching required for a project. The amount of patching should be recorded in square feet in the field and converted to square yards and tons in the office. While in the field, the Pavement designer should determine if a patch should be full-depth or partial depth.

Full-Depth Patches are defined as removing all PCC/AC material – surface, intermediate and base mixes, etc., by milling, carbide grinding or saw cutting, but not the granular or stabilized base/sub-base unless determined necessary by the field engineer.

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Partial Depth Patches are defined as removing a portion of the total PCC/AC thickness by milling or carbide grinding.

(a) Equipment and Supplies Needed

To perform a patching survey, the following equipment and supplies are needed: • Data Collection Sheets;

• Pencil;

• Clip Board;

• Hard Hat;

• Strobe Light;

• Vehicle;

• Map/Plan;

• Marking Paint

• Safety Vest; and

• Measuring Wheel.

• Camera

(b) Survey Procedure

Below are suggested steps to perform a patching survey:

Prepare data collection sheets to record type of distress, location, and type of patch. By performing this activity in the office, effort in the field can be concentrated on identifying locations that require patching.

Once the sheets have been prepared, go to the field with the equipment and supplies outlined above.

Establish the beginning of the project (paving joint, bridge joint, intersection, etc.) and mark Station 0+00 if no other stationing has been established. This stationing should be used to reference all field collected data (visual condition, coring/boring, FWD, etc.).

Walk the project and locate the areas requiring patching, milling or requiring a comment. If traffic control is being provided, traverse the pavement to assess the pavement condition and determine if patching, milling, etc. should be performed. If traffic control is not provided, then assess the pavement condition and determine if patching, milling, etc. should be performed from the shoulder. VDOT work zone safety procedures should be observed at all times. If walking the pavement is not possible due to safety or other reasons, the Pavement designer should request video logging of the pavement in order to perform a patching survey using a computer work station.

Once complete, the data can be entered into an EXCEL or similar spreadsheet to calculate the amount and type of patching, as well as milling quantities.

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For the preliminary analysis, only approximate pavement areas are required. For detailed analysis, more attention must be given to locating the patching and milling limits.

In addition, the Pavement designer should consider the pavement drainage conditions. This should include, but not be limited to: • Curb and gutter condition;

• Curb reveal;

• Shoulders;

• Underdrains;

• Side ditches; and

• Medians.

Finally, the Pavement designer should note any other pertinent information related to the project. Examples are poor roadway geometry, guardrail heights, bridge clearances, etc.

Guidelines for Determining Patch Types and Locations for AC Surfaces

Distress Type Severity Level

Milling (1" - 2") Comments

No Yes

AC Material Thickness

> 6" < 6"

Alligator Cracking 1 None None None

2 Partial Partial Full

3 Full Full Full

Rutting 1 None None None

2 Partial None None

3 Partial Partial Partial If Subgrade problem, patch full depth to include replacing all materials and repairing subgrade

Linear Cracking 1 None None None

2 None None None If crack is less than 1/2" wide and crack depth is less than 1/2 AC layer thickness, then crack fill.

2 Partial Partial Partial If the crack depth is greater than 1/2 AC layer thickness, then full depth patch.

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Guidelines for Determining Patch Types and Locations for AC Surfaces

Distress Type Severity Level

Milling (1" - 2") Comments

No Yes

AC Material Thickness

> 6" < 6"

Potholes/Failures/ N/A Partial None None Less than 6" in Diameter

Delaminations N/A Partial Partial Full Diameter is between 8" and 18"

N/A Full Full Full Diameter is greater than 18"

Bumps/Sags N/A None None None Causes low severity ride quality

N/A None None None Causes medium severity ride quality

N/A Full Full Full Causes high severity ride quality

Depression N/A None None None Less than 1" deep

N/A Partial None None Between 1" and 2" deep

N/A Full Full Full Greater than 2" deep

Patches N/A None None None Patch is in good condition and has little effect on ride quality

N/A Partial Partial Full Patch is in fair condition (exhibiting Severity 1 LDR Distresses) or is effecting ride quality.

N/A Full Full Full Patch is in poor condition (exhibiting Severity 2 or 3 LDR distresses).

Joint Reflection Cracking with Load

1 None None None Load transfer greater than 70%

Transfer greater than 70%

2 Partial None Partial Load transfer greater than 70%, use joint tape if AC layer thickness is less than 6" thick and milling will be performed

3 Partial Partial Partial Load transfer greater than 70%; patch to top of PCC Surface

Joint Reflection Cracking with Load

1 None None None Load transfer less than 70%

Transfer less than 70%

2 Full Full Full Load transfer is less than 70%; potential to reduce to partial depth patching, if needed

3 Full Full Full Load transfer less than 70%

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January 2018

Guidelines for Determining Patch Types and Locations for Concrete Pavement Surfaces

Distress Type Severity Comments

Low Medium High

Blow-Up Full Full Full

Corner Break None Full Full

Divided Slab None Full Full

Faulting None Full Full Consider grinding or undersealing the joint to remove fault.

Linear Cracking None None Full Consider grinding, undersealing or crack sealing for Low and Medium Severity.

Patching None ** Full Replace in kind – Type I, II or IV

Pumping None None Full Consider undersealing to correct Pumping

Punchout Full Full Full Type II patch if punchout greater that 6' long

Spalling AC AC Full Clean out spalled area and replace with AC

Full Depth Patches may be Type I, II or IV depending on pavement type and patching area. Refer to special provision on PCC patching

**: If LTE (Load Transfer Efficiency) < 70% - AC patch is not recommended (Use PCC patch)

If Mr subgrade is weak - PCC patch required

If Pumping is evident - PCC patch required

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January 2018

SECTION 602 – FALLING WEIGHT DEFLECTOMETER TESTING AND ANALYSIS GUIDELINES


One of the most difficult exercises for a Pavement designer is analyzing deflection data collected with a falling weight deflectometer. While FWDs have been in use for over 20 years, the methods to process the data are far from perfect. Engineers, educators and researchers are constantly trying to develop new analysis approaches that will provide data results that match field conditions with laboratory results.

Although most of the development has been in the field of pavement research, several software tools are available for production data processing and analysis. The purpose of this document is to provide guideline for engineers to follow when setting up FWD testing on a project and for analyzing results.

FWD data analysis is not an easy process, but with practice and experience engineers will be able to evaluate and determine how to use the FWD results.

SEC. 602.02 FWD TESTING

FWD testing shall be conducted in accordance with Virginia Test Method (VTM) 68 – Nondestructive Pavement Deflection Testing With a Falling-Weight-Type-Impulse Load Device.

SEC. 602.03 FWD DATA PROCESSING

In order to process FWD data, many steps are required. These steps include gathering information on the pavement’s surface condition, conducting a preliminary analysis on the deflection data, performing pavement coring and subgrade boring operations, processing of all the data collected, and analyzing, interpreting and reporting on the data results. Each one of these steps has numerous tasks associated with them. These steps are detailed in the following sections.

(a) Pavement Surface Condition Survey

Prior to collecting any FWD data, the Pavement designer will conduct a detailed pavement condition and patching survey. These surveys will help the Pavement designer establish possible problem areas with the pavement and set-up the appropriate FWD testing plan. The pavement condition survey, at a minimum, will:

Identify distress type, severity, extent and exact location,

Identify patched areas and areas that will probably require patching before or during the rehabilitation project, and

Use same linear referencing system as FWD data collection.

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Once these data are collected, the engineer can plot the results on a straight-line diagram. This will be extremely beneficial when other data are collected and analyzed.

(b) Preliminary Data Analysis

Once FWD data are collected, it is important to perform a preliminary analysis on the deflection data. The purpose of the preliminary analysis is to check sensor location and operation, data quality, and linearity of unbound pavement and subgrade layers.

(c) Pavement Coring and Subgrade Boring

In order to conduct an analysis of FWD data, the exact pavement structure must be known. For most roadways, the exact structure is not known; therefore, pavement coring is required. Also, while the engineer may know what type of subgrade soils exists in the project area, it cannot be assured without boring the subgrade and extracting samples. These materials collected in field can be analyzed in the lab, and the lab results used to validate FWD Data Analysis results.

For the materials above the subgrade, the coring and boring crew will record: • Layer Materials – Asphalt, PCC, Granular, Cement Treated, etc

• Layer Thickness – Thickness for each different layer

• Layer Condition – AC material stripped, PCC deteriorated, granular material contaminated, etc.

• Material Types – For AC Materials, identify various layer types

•

For the subgrade soils, adequate material shall be obtained in order to determine the following material properties in the lab: • Soil classifications (gradations and Atterberg Limits)

• Natural moisture content

• Lab CBR

• Resilient modulus (undisturbed or remolded)

• Unconfined Compressive Strength

(d) Full Data Processing

Once pavement condition data and materials data are collected, then the engineer can perform the data processing. The type of data processing depends on 1) pavement type – flexible, rigid or composite, and 2) testing performed – basin, joint load transfer, or corner void. Please refer to the “MODTAG-Users Manual and Technical Documentation” for further instructions.

(e) Data Analysis, Interpretation and Reporting

Except for operating the FWD processing programs, the data analysis and interpretation is the most difficult portion. Once the analysis and interpretation is completed, then the

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results must be presented in such a manner to be used in the pavement design programs. Please refer to the “MODTAG-Users Manual and Technical Documentation” for further information.

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January 2018

SECTION 603 – GUIDELINES FOR USE OF THE MECHANISTIC-EMPIRICAL PAVEMENT DESIGN

SEC. 603.01 PURPOSE

These guidelines are intended to aid professional staff knowledgeable in the field of pavement design and evaluation. Persons using these guidelines are responsible for their proper use and application in concert with the Mechanistic-Empirical Pavement Design (MEPDG) procedure using AASHTOware Pavement ME Software. Virginia Department of Transportation and individuals associated with the development of this guideline cannot be held responsible for improper use or application.

Mechanistic-Empirical (ME) pavement design utilizes theoretical pavement modeling and historical pavement performance data to predict pavement responses to a trial pavement structure rather than calculating a required layer thickness. Designers must first consider site conditions such as traffic, climate, subgrade and/or existing pavement conditions in creating a trial design and the software is used to predict the pavement distresses and smoothness. A trial design can be obtained from the Pavement Management System for a similar/nearby project or from personal/local experience or from any other pavement design software (such as Darwin, PaveXpress, Streetpave, Winpas, etc). The pavement responses are evaluated against performance criteria and reliability values. If the design does not meet the required performance criteria, it should be revised and the process repeated.

SEC. 603.02 PAVEMENT DESIGN

MEPDG shall be used for projects consisting of new construction, new alignment, pavement widening (lane addition) and reconstruction on Interstates and Primaries (including Limited Access). Reconstruction is defined as removal or manipulation of all bound layers and/or manipulation of bound and unbound base and subgrade. In addition, for Secondary Roadways, VDOT’s Secondary and Subdivision Design Guide will be used for new construction and reconstruction unless the traffic volumes exceed 10,000 AADT. If the traffic volume of the Secondary Roadway exceeds 10,000 AADT, the actual truck count and classification needs to be determined and serious consideration shall be given to designing using MEPDG for new construction and reconstruction. If truck classification is not available for the specific Secondary Roadway project, the statewide average given in the VDOT MEPDG user manual should be used. To aid the Pavement designer in utilizing the AASHTOware Pavement ME software to analyze a pavement structure, VDOT has developed a user manual which contains the required input parameters and step-by-step procedures. The Pavement designer shall follow this user manual to analyze pavement structures. The user manual can be found at the following link:

http://www.virginiadot.org/VDOT/Business/asset_upload_file287_3638.pdf

The District Materials Engineer has final approval on all Pavement Designs.

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Pavement Design Life

The following table provides the Design Life to be used for the pavement analysis.

Highway Classification Initial Construction Design (Years)

Interstate 30

Divided Primary Route 30

Undivided Primary Route 30

High Volume Secondary Route 30

Shoulder Design

Typically, paved shoulders have a pavement structural capacity less than the mainline; however, this is dependent on the roadway. For Interstate and Limited Access routes, the pavement shoulder shall have the same design depth of material as the mainline pavement. This will allow the shoulder to support extended periods of traffic loading as well as provide additional support to the mainline structure. A full-depth shoulder (same design depth of material as the mainline pavement) is also recommended for other high-volume non-interstate routes that are likely to be widened within the life of the mainline pavement.

Where a full-depth shoulder is not necessary, the shoulder’s pavement structure will be based on 2.5% of the mainline design AADTT (minimum) for the project following the AASHTO pavement design methodology. A minimum of two AC layers must be designed for the shoulder in order to provide edge support for the mainline pavement structure. The AC layers must be placed on an aggregate or cement stabilized aggregate layer, not directly on subgrade, to provide adequate support and drainage for the shoulder and mainline pavement structures. To help ensure positive subsurface drainage, the total pavement depth of the shoulder should be equal to the mainline structure (i.e. mainline pavement structure thickness above the subgrade is 20 inches, shoulder pavement structure thickness above the subgrade is 20 inches).

Drainage Considerations The presence of water within the pavement structure has a detrimental effect on the pavement performance under anticipated traffic loads. The following are guidelines to minimize these effects:

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January 2018

Standard UD-2 underdrains and outlets are required on all raised medians. UD-2 underdrains are intended to intercept water that may seep onto the pavement surface at the curb/pavement joint and create a safety hazard. Additionally, UD-2 underdrains can prevent water infiltration through or under the pavement structure. Refer to the current VDOT Road and Bridge Standards for installation details.

When Aggregate Base Material, Type I, Size #21-B is used as an untreated base or subbase, it shall be connected to a longitudinal pavement drain (UD-4) with outlets or day lighted (to the face of the ditch) to provide for positive lateral drainage on all roadways with a design ADT of 1,000 vehicles per day or greater. For super-elevated roadways where day lighting is used, only the lower/down side of the aggregate layer will be extended to the face of the ditch. (Refer to the current VDOT Road and Bridge Standards for installation details.) Other drainage layers can also be used. When the design ADT is less than a 1,000 vehicles per day, the Engineer must assess the potential for the presence of water and determine if sub-surface drainage provisions should be made.

When Aggregate Base Material, Size #21-A is used as an untreated base or subbase material, it will not be used to remove subsurface water by connecting it to a longitudinal underdrain.

Undercutting, transverse drains, stabilization, and special design surface and subsurface drainage installations will be considered whenever necessary to minimize the adverse impacts of subsurface water on the stability and strength of the pavement structure.

Standard CD-1 and CD-2 should be considered for use with all types of unstablized aggregates, independent of the traffic levels.

For roadways with a design ADT of 20,000 vehicles per day or greater, a stabilized drainage layer should be considered for placement on not less than 6 inches of stabilized aggregate material and connected to a UD-4 edge drain. Factors that may influence the selection of OGDL include constructability issues involving maintenance of traffic (e.g. multiple traffic shifts to complete pavement, etc.), numerous entrances that have to be maintained during construction, numerous intersecting streets, etc.

For additional information see Report Number FHWA-TS-80-224, Highway Sub-Drainage Design from the US Department of Transportation, Federal Highway Administration.

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January 2018

SECTION 604 – GUIDELINES FOR USE OF THE 1993 AASHTO PAVEMENT DESIGN PROCEDURE

SEC. 604.01 PURPOSE

These guidelines are intended to aid professional staff knowledgeable in the field of pavement design and evaluation. Persons using these guidelines are responsible for their proper use and application in concert with the AASHTO “Guide for Design of Pavement Structures – 1993”. Virginia Department of Transportation and individuals associated with the development of this guideline cannot be held responsible for improper use or application.

For rehabilitation projects, pavement designer shall use 1993 AASHTO.

SEC. 604.02 FLEXIBLE PAVEMENT DESIGN

A flexible pavement consists of asphalt concrete materials typically placed on aggregate base (stabilized or unstabilized) and subgrade. The flexible pavement system works to evenly distribute the loading to the subgrade to minimize the distresses.

Design Variables

Pavement Design Life Highway Classification Overlay Design

(Years)

Interstate 12

Divided Primary Route 12

Undivided Primary Route 12

High Volume Secondary Route 12

Farm to Market Secondary Route 10

Traffic Factors

Lane Distribution Factors Number of Lanes Per Direction VDOT Value for Pavement Design (%)

1 100

2 90

3 70

4 or more 60

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Traffic Growth Rate Calculation GR = [(AADTf / AADTi) (1/(F-I)) -1] x 100

Where:

GR = Growth Rate (%)

AADTf = Average annual daily traffic for future year

AADTi = Average annual daily traffic for initial year

I = Initial year for AADT

F = Future year for AADT

Future AADT Calculation If an AADT and growth rate is provided, then a future AADT can be calculated using the following equation:

AADTf = AADTI (1+GR/100)(F-I)

Where:



AADTi = Average annual daily traffic for initial year (year traffic data is provided)



ESAL Factors When no Weigh in Motion (WIM) or vehicle classification data are available to determine actual 18-kip Equivalent Single Axle Loads (ESAL) Factors, use the following values:

Vehicle Classification ESAL Factor (ESALs/vehicle)

Cars/Passenger Vehicles 0.0002

Single Unit Trucks 0.46

Tractor Trailer Trucks 1.05

If traffic classification or WIM data are available, use Appendix D of the 1993 AASHTO Design Guide for Pavement Structures to determine ESAL factors.

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ESAL Calculation For the ESAL calculation, use Compound Growth Factors. Assume the Growth in the ESAL Factor is 0%.

Directional Split For the directional split of truck traffic on a route, assume a 50/50 distribution unless information from Traffic Engineering or other sources are provided.

Reliability VDOT Value for Pavement Design

Highway Classification Urban Rural

Interstate 95 95

Divided Primary Route 90 90

Undivided Primary Route 90 85

High Volume Secondary Route 90 85

Farm to Market Secondary Route 85 75

Serviceability VDOT Value for Pavement Design

Highway Classification Initial Terminal

Interstate 4.2 3.0

Divided Primary Route 4.2 2.9

Undivided Primary Route 4.2 2.8

High Volume Secondary Route 4.2 2.8

Farm to Market Secondary Route 4.0 2.5

Standard Deviation For flexible pavements, the standard deviation of 0.49 shall be used.

Material Information

Structural Layer Coefficients (Rehabilitation and Overlay) Material Typical Value

SM-4.75

SM-9.0

.44

.44

SM-9.5 .44

SM-12.5 .44

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Material Typical Value

IM-19.0 .44

BM-25.0 .44

SMA 9.5, SMA 12.5, SMA 19.0 .44

Cold Central Plant Recycling (CCPR) mat.

Cold In-Place Recycling (CIR) materials

Graded Aggregate Base – 21A or 21B

.35

.35

.12

Cement Treated Aggregate Base .20

Cement Treated Soil (i.e.- soil cement) .18

Full Depth Reclamation (FDR) materials

Lime Treated Soil

.25

.18

Rubblized Concrete .18

Break and Seat/Crack and Seat Concrete .25

Gravel .10

Open Graded Drainage Layer – Bound .10

Open Graded Drainage Layer – Unbound 0 – .10

All other soils and subgrade improvements No Layer Coefficient

AC Material Layer Thickness Material Minimum Lift Thickness (in.) Maximum Lift Thickness (in.)

SM-4.75

SM-9.0

0.75

0.75

1.0

1.25

SM-9.5 1.25 1.5

SMA-9.5 1.25 1.5

SM-12.5 1.5 2

SMA-12.5 1.5 2

SMA-19.0 2 3 IM-19.0 2 3

BM-25.0 2.5 4

Asphalt OGDL 2 3

Cement OGDL 2 4

CCPRM 3 6

CIR 3 6

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FDR 6 12

NOTE: For normal application rate, reference Table 4 in Section 605.06.

Drainage Coefficients (m) For most designs, use a value of 1.0. If the quality of drainage is known as well as the period of time the pavement is exposed to levels approaching saturation, then refer to Table 2.4 in the 1993 AASHTO Guide for the Design of Pavement Structures.

Design Subgrade Resilient Modulus Resilient Modulus values for a soil may be obtained from laboratory testing, correlations to other soil properties, or from FWD testing. While there are numerous sources, caution must be used when selecting a design resilient modulus. An analysis of all the soils data will be conducted prior to selecting a value.

Laboratory Testing Results When laboratory testing is performed, an average Resilient Modulus (Mr) will not be used as the design Mr if the coefficient of variance (Cv) is greater than 10%. If the Cv is greater than 10%, then the Pavement designer will look at sections with similar Mr values and design those section based on that average Mr. If no sections clearly exist, then use the average Mr times 0.67 to obtain the design Mr. For those locations with an actual Mr less than the design Mr, then the Pavement designer will consider a separate design for that location or undercutting the area. More detailed procedures for using laboratory obtained Mr results will be contained in the future revision of this document.

Laboratory Correlations If resilient modulus results are not available from laboratory testing, then use the following correlations:

For fine-grained soils with a soaked CBR less than 10, use the following equation to correlate CBR to resilient modulus (Mr):

Design Mr (psi) = 1,500 x CBR

For non fine-grained soils with a soaked CBR greater than 10, use the following equation:

Mr = 3,000 x CBR 0.65

Typical values for fine-grained soils are 2,000 to 10,000 psi.

Typical values for coarse-grained soils are 10,000 to 20,000 psi.

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FWD Testing Results When FWD testing is conducted and the backcalculated resilient modulus is determined, use the following equation:

Design Mr = C x Backcalculated Mr

Where C = 0.33

Selecting Appropriate Mr Value The design of flexible pavements is extremely sensitive to the design Mr value. The engineer must select the appropriate Mr value to ensure the pavement is not under or over designed. When no laboratory or FWD results are available, the Pavement designer should use the Mr results based on the correlation to the CBR values. If results from FWD testing are available, then the Pavement designer should use these results. CBR data can be used to validate the FWD results; material with a high CBR should have a high resilient modulus; material with a low CBR should have a low resilient modulus. If laboratory results exist and represent all of the soils to be encountered on the project, then these results should be used. If the results do not cover the entire project, then FWD results and laboratory correlations should supplement the laboratory results.

For all pavement designs, if the Design Mr is greater than 15,000 psi, then use a Design Mr value of 15,000 psi. This will prevent the over estimation of the subgrade strength which would lead to a potential pavement underdesign.

Shoulder Design Typically, paved shoulders have a pavement structural capacity less than the mainline; however, this is dependent on the roadway. For Interstate and Limited Access routes, the pavement shoulder shall have the same design depth of material as the mainline pavement. This will allow the shoulder to support extended periods of traffic loading as well as provide additional support to the mainline structure. A full-depth shoulder (same design depth of material as the mainline pavement) is also recommended for other high-volume non-interstate routes that are likely to be widened within the life of the mainline pavement.

Where a full-depth shoulder is not necessary, the shoulder’s pavement structure will be based on 2.5% of the mainline design ESALs (minimum) for the project following the AASHTO pavement design methodology. A minimum of two AC layers must be designed for the shoulder in order to provide edge support for the mainline pavement structure. The AC layers must be placed on an aggregate or cement stabilized aggregate layer, not directly on subgrade, to provide adequate support and drainage for the shoulder and mainline pavement structures. To help ensure positive subsurface drainage, the total pavement depth of the shoulder should be equal to the mainline structure (i.e. mainline

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pavement structure thickness above the subgrade is 20 inches, shoulder pavement structure thickness above the subgrade is 20 inches).



When Aggregate Base Material, Type I, Size #21-B is used as an untreated base or subbase, it shall be connected to a longitudinal pavement drain (UD-4) with outlets or day lighted (to the face of the ditch) to provide for positive lateral drainage on all roadways with a design ADT of 1,000 vehicles per day or greater. For super-elevated roadways where day lighting is used, only the lower/down side of the aggregate layer will be extended to the face of the ditch. (Refer to the current VDOT Road and Bridge Standards for installation details.) Other drainage layers can also be used. When the design ADT is less than a 1,000 vehicles per day, the Engineer must assess the potential for the presence of water and determine if sub-surface drainage provisions should be made.

When Aggregate Base Material, Size #21-A is used as an untreated base or subbase material, it will not be used to remove subsurface water by connecting it to a longitudinal underdrain.

Undercutting, transverse drains, stabilization, and special design surface and subsurface drainage installations will be considered whenever necessary to minimize the adverse impacts of subsurface water on the stability and strength of the pavement structure.

Standard CD-1 and CD-2 should be considered for use with all types of unstablized aggregates, independent of the traffic levels.


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SEC. 604.03 RIGID PAVEMENT DESIGN

In a rigid pavement system, the pavement layer(s) is composed of materials of high rigidity and high elastic moduli which distributes a low level of stress over a wide area of the subgrade soil. Consequently, the major factor considered in the thickness design of rigid pavements is the structural strength of the pavement layers(s); i.e. – the concrete itself. Rigid pavements are classified into jointed and continuously reinforced. A jointed plain concrete pavement is an unreinforced pavement structure with joints at certain designated intervals to compensate for expansion and contraction forces and thermally induced stresses. Continuously reinforced concrete pavements, on the other hand, have been designed with sufficient reinforcement to eliminate the need for joints.

Design Variables

Pavement Design Life

Highway Classification

AC Overlay Design

(Years)

PCC Overlay Design

(Years)

Interstate 10 30




Standard Deviation For rigid pavements, a standard deviation of 0.39 shall be used.

Traffic Factors

Lane Distribution Factors Number of Lanes Per Direction VDOT Value for Pavement Design (%)

1 100

2 90

3 70

4 or more 60

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Traffic Growth Rate Calculation GR = [(AADTf / AADTi) (1/(F-I)) -1] x 100

Where:



AADTi = Average annual daily traffic for initial year



Future ADT Calculation If an AADT and growth rate is provided, then a future AADT can be calculated using the following equation:

AADTf = AADTI (1+GR/100)(F-I)

Where:



AADTi = Average annual daily traffic for initial year (year traffic data is provided)



ESAL Factors When no Weigh in Motion (WIM) or vehicle classification data are available to determine actual 18-kip Equivalent Single Axle Loads (ESAL) Factors, use the following values:

Vehicle Classification ESAL Factor (ESALs/Vehicle)

Cars/Passenger Vehicles 0.0003

Single Unit Trucks 0.59

Tractor Trailer Trucks 1.59

ESAL Calculation For the ESAL Calculation, use Compound Growth Factors. Assume Truck Growth ESAL Factor is 0%.

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Directional Split For the directional split of truck traffic on a route, assume a 50/50 distribution unless information from Traffic Engineering or other sources are provided.

Reliability VDOT Value for Pavement Design (%)

Highway Classification Urban Rural

Interstate 95 95




Serviceability VDOT Value for Pavement Design

Highway Classification Initial Terminal

Interstate 4.5 3.0

Divided Primary Route 4.5 2.9

Undivided Primary Route 4.5 2.8

High Volume Secondary Route 4.5 2.8

Material Information

28-Day Mean PCC Modulus of Rupture (psi) Typical Range – 600 to 800 VDOT Value for Pavement Design – 650

Use default value if actual value is not available. Where possible, use value based on historical data.

28-Day Mean PCC Modulus of Elasticity (psi) Typical Range – 3,000,000 to 8,000,000 VDOT Value for Pavement Design – 5,000,000

Use default value if actual value is not available. Where possible, use value based on historical data.

Mean Effective k-value (psi/inch) Typical Range – 50 to 500 VDOT Value for Pavement Design – 250

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If the subgrade resilient modulus is known from FWD testing or obtained from correlation with CBR testing, then use the following equation:

k-value = Mr / 19.4

Caution must be used when selecting a design k-value based on resilient modulus and CBR. An analysis of all the soils data should be conducted prior to selecting a value. An average Resilient Modulus (Mr) should not be used as the design Mr if the coefficient of variance (Cv) is greater than 10%. If the Cv is greater than 10%, then the Pavement designer should look at sections with similar Mr values and design those section based on that average Mr. If no sections clearly exist, then use the average Mr times 67% to obtain the design Mr. For those locations with an actual Mr less than the design Mr, then the Pavement designer should consider a separate design for that location or undercutting the area.

If the k-value is obtained from backcalculation, then use this value.

If the k-value (based on backcalculation or subgrade resilient modulus) is larger than 500, then use 500 as the design value.

Subdrainage Coefficient For most designs, use a value of 1.0. If the quality of drainage is known as well as the period of time the pavement is exposed to levels approaching saturation, then refer to Table 2.4 in the 1993 AASHTO Guide for the Design of Pavement Structures.

Load Transfer Factors

Unbonded PCC Overlays with Load Transfer Devices VDOT Value for Design

Pavement Type Asphalt Shoulder Tied PCC Shoulder or Wide Lane

Jointed Plain 3.2 2.7

Continuously Reinforced

3.0 2.6

Overlays Designs on Existing Pavements For AC overlays on existing PCC pavements, existing composite pavements, and bonded PCC overlays, determine the appropriate J-Factor based on the load transfer efficiency determined from joint/crack testing.

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Pavement Type Load Transfer Efficiency Design J-Factor

Jointed Plain; AC/JPCP > 70% 3.2

50 – 70% 3.5

< 50% 4.0

Jointed Reinforced; AC/JRCP

> 70% 3.2

50 – 70% 3.5

< 50% 4.0

Continuously Reinforced; AC/CRCP

2.4 (working cracks repaired with CRCP)

Shoulder Design Typically, paved shoulders have a pavement structural capacity less than the mainline; however, this is dependent on the roadway. For Interstate and Limited Access, the pavement shoulder shall have the same design as the mainline pavement. This will allow the shoulder to support extended periods of traffic loading as well as provide additional support to the mainline structure. A full-depth shoulder (same design as the mainline pavement) is also recommended for other high-volume non-interstate routes that are likely to be widened within the life of the mainline pavement.

Two types of shoulders are designed for Portland cement concrete highways – full-width concrete shoulders, narrow-width concrete section with an asphalt concrete extension, or an asphalt shoulder. For full-width concrete shoulders, the pavement shoulder shall have the same design as the mainline pavement. This will allow the shoulder to support extended periods of traffic loading as well as provide additional support to the mainline structure.

A narrow-width concrete section with an asphalt concrete extension shoulder is constructed when a wide concrete lane (14 feet) is part of the mainline pavement. Twelve feet of the fourteen-foot wide slab is part of the outside travel lane, the remaining two feet is striped and designated as part of the shoulder. The two-foot section of concrete has the same structure as the twelve-foot section; therefore, no separate pavement design is necessary. For the asphalt concrete portion of the shoulder and other asphalt concrete shoulders not located on Interstates or high-volume routes, the shoulder’s pavement structure should be based on 2.5% of the design ESALs (minimum) for the project following the AASHTO pavement design methodology. A minimum of two AC layers must be designed for the shoulder. The AC layers must be placed on an aggregate or cement stabilized aggregate layer, not directly on subgrade, to provide adequate support and drainage for the shoulder structure. To help ensure positive subsurface drainage, the total pavement depth of the shoulder should be equal to the mainline structure (i.e.

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mainline pavement structure thickness above the subgrade is 20 inches, shoulder pavement structure thickness above the subgrade is 20 inches). When the asphalt shoulder is constructed on an Interstate or high-volume roadway, the depth of the asphalt layers shall be the same as the depth of the Portland Cement Concrete slab.



When Aggregate Base Material, Type I, Size #21-B is used as an untreated base or subbase, it shall be connected to a longitudinal pavement drain (UD-4) with outlets or day lighted (to the face of the ditch) to provide for positive lateral drainage on all roadways with a design ADT of 1,000 vehicles per day or greater. For super-elevated roadways where day-lighting is used, only the lower/down side of the aggregate layer will be extended to the face of the ditch. (Refer to the current VDOT Road and Bridge Standards for installation details.) Other drainage layers can also be used. When the design ADT is less than a 1,000 vehicles per day, the Engineer must assess the potential for the presence of water and determine if sub-surface drainage provisions should be made.

When Aggregate Base Material, Size #21-A is used as an untreated base or subbase material, it should not be used to remove subsurface water by connecting it to a longitudinal underdrain.

Undercutting, transverse drains, stabilization, and special design surface and subsurface drainage installations should be considered whenever necessary to minimize the adverse impacts of subsurface water on the stability and strength of the pavement structure.

Standard CD-1 and CD-2 will be considered for use with all types of unstablized aggregates, independent of the traffic levels.


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1. Fill Slope 12. Shoulder Base

2. Original Ground 13. Pavement Cross Slope

3. Curb or Curb and Gutter 14. Subgrade

4. Select Material or Prepared Roadbed 15. Roadbed Soil

5. Shoulder Surfacing 16. Pavement Structure

6. Subbase 17. Shoulder Cross Slope

7. Base Course 18. Travel Lanes

8. Surface Course 19. Shoulder

9. Pavement Slab 20. Roadway

10. Ditch Front Slope 21. Roadbed

11. Cut Slope Diagram 1 – Pavement Definitions

Flexible Pavement Rigid Pavement

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SECTION 605 – ASPHALT CONCRETE MIX SELECTION GUIDELINES

SEC. 605.01 PURPOSE OF GUIDELINES

The guidelines provided herein are intended to aid the user in recommending mix types for asphalt overlays of flexible and rigid pavement, and new construction based on specific traffic and environmental conditions expected. These guidelines should be used as part of, or in conjunction with an engineering analysis of the pavement section. These guidelines are not intended to address pavement distress mechanisms, structural inadequacy of the pavement, existing pavement defects, or other types of pavement deficiencies. It is the responsibility of the user to conduct an analysis/evaluation of the existing or expected pavement conditions prior to using this guide. Failure to do so could significantly affect the performance and service life of the materials and mixes selected.

These guidelines are applicable to VDOT maintenance and new construction projects. While the guidelines could be used for non-VDOT work with similar conditions, experience and engineering judgment should be exercised for such application.

These guidelines indicate the general highway conditions under which each mix should be used. Generally, a single mix type is used for all lanes in a single direction of a roadway. The asphalt binder type may be selected based on the Average Annual Daily Truck Traffic (AADTT) range in the design direction for construction and maintenance projects. The asphalt binder type AADTT range is based on the one way annual average daily truck traffic in the design direction. AADTT is used in conjunction with the mix type’s nominal maximum aggregate size in this guide. Traffic speed, vehicle types and volume should also be considered in the selection of a mix type. These considerations may warrant the use of a stiffer binder. Experience and judgment should be used in selecting the appropriate mixes to be used. Each District may implement a simple guide chart to eliminate those mixes that are not needed in their area.

SEC. 605.02 DESCRIPTION OF ASPHALT CONCRETE MIXES

Numerous asphalt mixes are used in Virginia. These mixes are designed to perform different functions within the pavement structure. Mixes vary based on nominal maximum aggregate size, aggregate gradation, asphalt binder content and other variables just to name a few. The following sections describe common asphalt mixes, dense graded and gap graded, used in Virginia, in addition to specialty mixes that have been used in select situations.

(a) Dense Graded Mixes

Dense graded mixes, also known as SUPERPAVE™ in Virginia, are asphalt mixes with a uniform distribution of aggregate sizes along the maximum density line. These mixes can be “fine” or “coarse” graded depending on whether the aggregate gradations are above or below the maximum density line. Dense graded mixes are identified based on the nominal

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maximum aggregate size. The nominal maximum aggregate size is defined as one sieve size larger than the first sieve to retain more than 10 percent aggregate as shown in the design range specified in Section 211.03, Table II-13 of the Road and Bridge Specifications. [It is important to note that while Virginia uses US Customary units for constructing projects, asphalt mixes are identified based on the metric sieve equivalent (i.e. 9.5mm, 12.5mm, 19.0mm and 25.0mm).] Three different families of dense graded mixes are used in Virginia – surface, intermediate, and base. A description of each family and the associated asphalt mix(s) are provided in the following sections.

(1) Surface Mixes Surface mixes serve as both functional and structural layers of the pavement structure. Surface mixes are directly exposed to traffic and the environment. They must provide a smooth, stable, safe (i.e. skid resistance) riding surface, and promote surface water drainage. In addition, they serve to prevent the entrance of excessive quantities of water into the underlying Hot Mix Asphalt (HMA) layers, bases, and subgrade. The surface layer normally contains the highest quality materials. In most instances, only one surface mix lift will be placed on a project. VDOT has three predominant dense graded surface mixes. Surface mixes are given the SM-XY.Z designation in contracts, specifications, and special provisions where SM stands for surface mix and XY.Z denotes the nominal maximum aggregate size.

SM-4.75 This mix is a ‘very fine’ (3/16 inch [4.75 mm] nominal maximum aggregate size) surface mix generally placed at 3/4 inch (19 mm) to 1 inch thickness. This mix is generally used in subdivisions and low volume pavements with little or no heavy vehicle traffic (trucks, buses) as a final riding surface. However, this can be considered for other situations on case by case basis. This mix should never be placed directly on aggregate base material; it is recommended to be placed on a minimum of 2 inches (50 mm) of a larger nominal maximum aggregate surface, intermediate, or base mix.

SM-9.0 This mix is a ‘fine’ (3/8 inch [9.5 mm] nominal maximum aggregate size) surface mix generally placed at 1 inch (25 mm) thickness. This mix is generally used in subdivisions and low volume pavements with little or no heavy vehicle traffic (trucks, buses) as a final riding surface. However, this can be considered for other situations on case by case basis. This mix should never be placed directly on aggregate base material; it is recommended to be placed on a minimum of 2 inches (50 mm) of a larger nominal maximum aggregate surface, intermediate, or base mix.

SM-9.5 This mix is a ‘fine’ to ‘medium’ (3/8 inch [9.5 mm] nominal maximum aggregate size) surface mix generally placed at 1 ½ inches (40 mm) thickness. SM-9.5 mixes usually result in low water permeability values. This mix tends to be less susceptible to segregation than the SM-12.5 mix type described below. SM-9.5

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surface mixes can be considered the desired surface mix and are recommended for most final surface applications.

SM-12.5 This mix is a ‘medium’ to ‘coarse’ (½ inch [12.5 mm] nominal maximum aggregate size) surface mix generally placed at 2 inches (50 mm) thickness. Depending on the aggregate gradation, this mix is more suited for roadways that need additional structural capacity to handle traffic loads. This mix tends to have higher permeability values when compared to a SM-9.5.

SM-19.0 This mix is a ‘coarse’ (3/4 inch [19.0 mm] nominal maximum aggregate size) mix generally placed at 2 inches (50 mm) thickness. In certain cases where structure is of a prime concern or traffic loadings are extreme, this mixture may be used as a final surface course.

(2) Intermediate Mix

The intermediate mix, sometimes called binder course, consists of one or more lifts of structural asphalt concrete placed below the surface layer. Its purpose is to distribute traffic loads so that stresses transmitted to the pavement foundation will not result in permanent deformation of that layer. Additionally, it facilitates the construction of the surface layer. Designed with larger aggregates, the intermediate layer is intended to provide resistance to rutting and to intercept top-down fatigue cracking. In most instances, only one intermediate mix lift will be used on a project. Intermediate mixes are given the IM-XY.Z designation in contracts, specifications and special provisions where IM stands for intermediate mix and XY.Z denote the nominal maximum aggregate size.

IM-19.0 This mix is a ‘coarse’ (3/4 inch [19.0 mm] nominal maximum aggregate size) mix generally placed at 2 inches (50 mm) thickness. This mix can handle public traffic during construction for an extended period of time and allows for later application of a surface mix to provide a final wearing surface.

(3) Base Mix As the name implies, the base mix is the base asphalt layer for the pavement structure. Its major function is to provide the principal support of the pavement structure. The base mix uses the largest aggregate particles to provide resistance to rutting and to bottom-up fatigue cracking. Unlike surface mixes, more than one lift of base mix may be placed on a project to obtain the designed base layer thickness. Base mixes are given the BM-XY.Z designation in contracts, specifications, and special provisions where BM stands for base mix and XY.Z denotes the nominal maximum aggregate size.

BM-25.0 This mix is a 1 inch (25.0 mm) nominal maximum aggregate size mix generally placed at 3 inches (75 mm) or greater thickness. Depending on the aggregate gradations and placement procedures, this base does not usually require

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placement of an intermediate course to provide a platform for placement of a smooth wearing surface. Public traffic should not be permitted on this material for extended periods of time without restrictions.

(b) Gap Graded Mixes

Gap graded mixes, are asphalt mixes with a non-uniform distribution of aggregate sizes. These mixes contain aggregates retained on the upper and lower sieves, but with little aggregate retained on the middle sieves. As with dense graded mixes, gap graded mixes are identified based on the nominal maximum aggregate size.

Stone Matrix Asphalt (SMA) is the typical gap graded mix used in Virginia. SMA is composed of a gap-graded aggregate that maximizes rutting resistance and durability with a stable stone-on-stone skeleton held together by a rich mixture of asphalt binder (specified PG grading), filler and stabilizing agents such as fibers. This mix is for use on heavy to extreme heavy traffic volume routes where the expected higher cost can be justified with improved performance over other mixes. SMAs are recommended for placements of a minimum of 5,000 tons and only in heavy traffic conditions due to their higher cost and special considerations in their design, production, and placement.

Two families of SMA mixes are used in Virginia – surface and intermediate. A description of each family and the associated asphalt mix(s) are provided in the following section. All gap graded mixes are given the designation SMA-XY.Z(binder type) in contracts, specifications and special provisions where SMA stands for stone matrix asphalt, XY.Z denotes the nominal maximum aggregate size, and (binder type) denotes the binder to be used.

(1) Surface Mixes VDOT has two SMA surface mixes.

SMA-9.5 This mix is a ‘fine’ to ‘medium’ (3/8 inch [9.5 mm] nominal maximum aggregate size) surface mix generally placed at 1 ½ inches (40 mm) thickness. SMA 9.5 surface mix is recommended for final surface applications on high traffic volume and high truck volume routes.

SMA-12.5 This mix is a ‘medium’ (½ inch [12.5 mm] nominal maximum aggregate size) surface mix generally placed at 2 inches (50 mm) thickness. SMA 12.5 surface mix is recommended for final surface applications on high traffic volume and high truck volume routes. This mix may be used in lieu of SMA-19.0 as an intermediate SMA layer.

(2) Intermediate Mix In most instances, only one intermediate mix lift will be used on a project. When rigid pavement is overlaid, more than one intermediate mix lift may be used.

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SMA-19.0 This mix is a ‘medium’ to ‘coarse’ (¾ inch [19.0 mm] nominal maximum aggregate size) mix generally placed at 2 inches (50 mm) thickness. SMA 19.0 mixes are recommended for intermediate applications on high traffic volume and high truck volume routes.

(3) Base Mix VDOT does not have any SMA Base Mix designation. If a base mix is desired for use with SMA, use a dense graded Base mix.

(c) Specialty Mixes While the vast majority of asphalt placed in Virginia is either dense graded or gap graded, VDOT does use some specialty mixes. These mixes are designed to provide specific functions in the pavement structure. Below is a description of mixes Virginia has used on its roadway network.

Thin Hot Mix Asphalt Overlay (THMACO) This mix is a ‘fine’ to ‘medium’ (3/8 inch [9.5 mm] nominal maximum aggregate size) surface mix generally placed at 3/4 inch (19 mm) thickness. THMACO is a gap graded hot mix asphalt used for final surface applications as a functional overlay on flexible and rigid pavements. THMACO is primarily used for pavement preservation.

Open Graded Drainage Layer (OGDL) is a ‘medium’ (¾ inch [19.0 mm] nominal maximum aggregate size) mix generally placed at 2 inches (50 mm) thickness. This mix has very little fine aggregate material to allow for the movement of water. It is used as part of a pavement drainage system. Guidelines on use of OGDL can be found in Section 604.

BM-25.0 With Increased Asphalt Content This mix may be designated as BM-25.0D+0.4 or BM-25.0D+0.8 (also referenced as High Modulus, High Binder Base Mix). This mix is intended to have higher asphalt content than the standard BM-25.0 to provide better crack resistance while maintaining the ability to resist rutting.

Cold Central Plant Recycling Material (CCPRM) CCPRM can be used on projects that include both new construction and rehabilitation. CCPRM is intended to be used as a replacement of bound and unbound materials within a new or existing flexible or composite pavement system. When it is intended to replace asphalt mixes, CCPRM will typically be used as a substitute for BM-25.0. At no time should CCPRM be used as the final riding surface. CCPRM is typically applied at 3 to 6 inch lift thickness; multiple lifts can be placed for depths exceeding 6 inches. See Section 608 of the Materials Division’s Manual of Instruction for additional details on pavement design using CCPRM.

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Stabilized (S) mix designation indicates the use of a PG 64S-22 binder with an approved stabilizing additive from the Department’s approved list in the Materials Division Manual of Instructions. This designation can be used in extreme traffic loading situations. This designation does not provide resistance to reflective cracking. This designation should only be combined with ‘A’ mixes.

(d) Parking Lot Porous Pavement Mix For Parking Lot Applications, VDOT has recently constructed a Porous Pavement using Porous Asphalt Mix (PAM). Porous Pavements provide an opportunity to manage stormwater runoff. Similar to an OGDL in that water will pass through the asphalt mixtures used, the difference is that the entire pavement structure, including the stone reservoir, allows for movement of water through the entire pavement structure and into the underlying subgrade or into a collection basin. Generally, the two PAM mixes used are:

Porous Asphalt Mix 9.5 (PAM-9.5) This mix is a ‘fine’(3/8 inch [9.5 mm] aggregate size) surface mix placed at 1.5 inch (37 mm) thickness. PAM-9.5 is an open graded asphalt mix applied atop porous asphalt or conventional pavement structure used for drainage.

Porous Asphalt Mix 19.0 (PAM-19.0) This mix is a ‘medium’ (3/4 inch [19.0 mm] aggregate size) base mix placed at 3.0 inch (75 mm) thickness. PAM-19.0 is an open graded asphalt mix applied atop a stone reservoir in a porous pavement structure.

SEC. 605.03 VDOT ASPHALT BINDERS

As with the asphalt mixes, VDOT typically uses letters to designate asphalt binders in contracts, specifications and special provisions. For dense graded mixes, asphalt binder designations A, D, and E are used. Mix stiffness generally increases from ‘A’ to ‘E’, with ‘A’ being the softest. For gap graded asphalt concrete, no letter designation is used in contracts, specifications, and special provisions. In the specifications and special provisions for specialty mixes, the asphalt binder is declared. The following sections define each asphalt binder.

(a) Dense Graded Mix Binder Letter Designations

‘A’ - The ‘A’ designation corresponds with a Performance Graded (PG) asphalt binder of PG 64S-22 (formerly PG 64-22). This designation should perform well in low to medium traffic loading situations.

‘D’ - The ‘D’ designation corresponds with a Performance Graded (PG) asphalt binder of PG 64H-22 (formerly PG 70-22). This designation should perform well in medium to high traffic loading situations.

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‘E’ - The ‘E’ designation corresponds with a Performance Graded (PG) asphalt binder of PG 64E-22 (formerly PG 76-22). Mixes with this binder designation should perform well in high to extremely high traffic loading situations. The stiffness of mixes using this binder should not be used as a substitute for deficient pavement structure (high deflections under traffic loadings will destroy any pavement structure). In general applications, the ‘E’ binder designation is not used in a base mix.

(b) Gap Graded and Specialty HMA Binders

PG 64H-22 – Like the ‘D’ designation for dense graded mixes, this binder is the Performance Graded (PG) 64H-22 (formerly PG 70-22). This designation should perform well in medium to high traffic loading situations and over continuously reinforced concrete pavement.

PG 64E-22 – Like the ‘E’ designation for dense graded mixes, this binder is the Performance Graded (PG) 64E-22 (formerly PG 76-22). These designations should perform well in high to extremely high traffic loading situations and over jointed concrete pavement. The stiffness of this mix should not be used as a substitute for deficient pavement structure (high deflections under traffic loadings will destroy any pavement structure).

PG 64V-28 – This binder is a polymer modified Performance Graded (PG) 64V-28 (formerly PG 70-28). The purpose of this binder is to resist thermal cracking and minimize reflective cracking over jointed concrete pavement.

SEC. 605.04 ASPHALT MIX SELECTION – GENERAL APPLICATIONS

When making a determination regarding which asphalt mix type to use, the AADTT and the pavement type must be known (new construction, existing flexible pavement, or existing rigid pavement). .

NOTE: Gap graded mixes generally outperform conventional mixes, therefore, justifying the additional cost for the gap graded mixes.

(a) Asphalt Binder Selection

For new construction, major rehab projects or maintenance projects this section provides guidance for selecting binder and mix designations based on readily available traffic data. Since the truck traffic impacts the binder and mix utilization the most, the one way annual average daily truck traffic in the design direction is used for selecting binder and mix designation. The Annual Average Daily Traffic (AADT) and percentage of trucks are readily available from traffic engineering for any section/route. The Average Annual Daily Truck Traffic (AADTT) is calculated by multiplying the AADT by the truck percentage in the design direction. Depending on the availability of 1 or 2 way AADT and

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traffic directional distribution factor (for 2 way AADT), AADTT in the design direction can be calculated in any of the following manners:

AADTT = 2 way AADT * % truck * directional traffic distribution factor

AADTT = 2 way AADT * % truck * 0.5, (in lieu of directional traffic distribution factor)

AADTT = 1 way AADT * % truck

Once the one-way AADTT in known, Tables 1 through 3 summarize the binder selection process based on pavement layer and pavement type. These tables reflect the prevailing practice of the most commonly used mixes and do not necessarily preclude the use of other mixes not listed herein on a case-by-case basis.

(b) Asphalt Mix Selection

During the pavement evaluation and design process, a total asphalt thickness is determined. From this thickness, a series of asphalt lifts are used to construct the pavement structure. For the base layer, one or more lifts may be required. VDOT has one base mix, BM-25.0, for use in construction, reconstruction, or major rehabilitation.

VDOT has two intermediate and five surface mixes for use in construction, reconstruction, or rehabilitation. Tables 1 through 3 summarize the mixes available for various layers based on AADTT and pavement type.

Table 1 –Surface Mix Selection

AADTT1

Mix Designation

Flexible Pavements Rigid Pavement Overlays

0 - 299 SM-4.75A, SM-9.0A, SM-9.5A or SM-12.5A

SM-9.5D or SM-12.5D

300 - 9992 SM-9.5D or SM-12.5D SM-9.5E or SM-12.5E

1000 – 24993 SM-9.5E, SM-12.5E, SMA-9.5(64H-22) or SMA-12.5(64H-22)

SM-9.5E, SM-12.5E, SMA-9.5(64H-22), or SMA-12.5(64H-22)

> 2500 SMA-9.5(64E-22) or SMA-12.5(64E-22)

SMA-9.5(64E-22) or SMA-12.5(64E-22)

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1. AADTT = AADT x Percent Trucks in the design direction

2. For Rigid Pavement Overlays, ‘D’ designated mixes may be considered on Continuously Reinforced Pavement

3. Consideration to using Gap Graded Surface Mix is strongly recommended, especially on limited access facilities and on Rigid Pavement Overlays.

Note 1: For preventative maintenance applications, consideration to using a SM-4.75, SM-9.0, or THMACO (high volume applications) should be considered.

Note 2: District Materials Engineer should be consulted when ‘E’ designated mixes are being considered in small quantities, due to possible limited liquid storage at a plant and to cost.

Table 2 –Intermediate Mix Selection

AADTT1

Mix Designation


0 – 299 IM-19.0A IM-19.0D

300 - 9992 IM-19.0D IM-19.0E

1000 – 24993 IM-19.0D, SMA-19.0 (64H-22)* IM-19.0E, SMA-19.0 (64E-22)*

> 2500 SMA-19.0 (64E-22)* SMA-19.0 (64E-22)*


2. For Rigid Pavement Overlays, ‘D’ designated mixes may be considered on Continuously Reinforced Pavement

3. Consideration to using Gap Graded Surface Mix is strongly recommended, especially on limited access facilities.

Note 1: District Materials Engineer should be consulted when ‘E’ designated mixes are being considered in small quantities, due to possible limited liquid storage at a plant and to cost.

* An SMA-12.5 may be used in lieu of SMA-19.0.

Table 3 –Base Mix Selection

AADTT1

Mix Designation


0 to 999 BM-25.0A BM-25.0A

> 1000 BM-25.0D BM-25.0D

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SEC. 605.05 ASPHALT BINDER AND MIX SELECTION – SPECIALIZED

LOCATIONS

There will be times when a designer needs to select binder and mix types in areas with high truck percentages and slow speeds, excessive grades (>6%) and standing traffic, all of which result in extreme pavement loadings. Some examples of these areas are truck climbing lanes, quarry roads, and truck parking areas. In these situations, the designer should select a binder with high stiffness to resist movement under load. To aid the designer, Table 4 lists the mixes that can be used in the extreme loading situations.

Table 4 – Specialized Pavement Locations

Mix Type Surface Intermediate Base

Truck Climbing Lane and Roads with Excessive Grades (>6%)

SM-9.5E IM-19.0D BM-25.0D

SM-12.5E IM-19.0E

SM-19.0D SMA-19.0 (64E-22)

SMA-9.5 (64E-22)

SMA-12.5 (64E-22)

Industrial Route, Quarry

SM-9.5D IM-19.0D BM-25.0D

SM-9.5E IM-19.0E

SM-12.5D

SM-12.5E

Truck Parking Area SM-9.5E IM-19.0D BM-25.0D

SM-12.5E IM-19.0E

Intersections and Railroad Crossings with Moderate to Heavy

Truck Percentage

SM-9.5E IM-19.0E BM-25.0D

SM-12.5E

Heavy Urban Traffic

with Buses

SM-9.5E IM-19.0D BM-25.0D

SM-12.5E IM-19.0E

Porous Parking Lots PAM-9.5 PAM-19.0

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SEC. 605.06 APPLICATION RATES

The normal application rate for a single lift thickness for the various mixes is shown in Table 5. Deviations to the normal application rate should be done in accordance with Section 315.05 (c) of the Road and Bridge Specifications.

Table 4 – VDOT Mix Comparison Table

Asphalt Concrete Mixes Nominal Maximum Aggregate Size Normal Application Rate Note 1

Surface Mix

SM-4.75 3/16 inch

(4.75 mm)

3/4 inch – 90 lb/ yd2

(19.0 mm – 49 kg/m2)

SM-9.0 3/8 inch

(9.5 mm)

1 inch – 110 lb/ yd2

(25.0 mm – 60 kg/m2)

SM-9.5 3/8 inch

(9.5 mm)

1.5 inch - 165 lb/yd2

(40.0 mm – 90 kg/m2)

SM-12.5 1/2 inch

(12.5 mm)

2.0 inch - 220 lb/yd2

(50.0 mm – 125 kg/m2)

SM-19.0 3/4 inch

(19.0 mm)

2.0 inch – 220 lb/yd2

(50.0 mm – 125 kg/m2)

SMA-9.5 3/8 inch

(9.5 mm) 1.5 inch - 165 lb/yd2

(40.0 mm – 90 kg/m2)

SMA-12.5 1/2 inch

(12.5 mm)

2.0 inch - 220 lb/yd2

(50.0 mm – 125 kg/m2)

Intermediate Mix

SMA 19.0 (intermediate) 1/2 to 1 inch

(12.5 to 19.0mm)Note 2 2 inch – 220 lb/yd2

(50.0 mm – 125 kg/m2)

IM-19.0 3/4 inch

(19.0 mm)

2 inch – 220 lb/yd2

(50.0 mm – 125 kg/m2)

Base Mix

BM-25.0 1 inch

(25.0 mm)

3.0 inchNote 3

(75.0 mm)

Open Graded Drainage Layer

OGDL -- 2.0 inch

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Asphalt Concrete Mixes Nominal Maximum Aggregate Size Normal Application Rate Note 1

Surface Mix

(50 mm)

Thin Hot Mix Asphalt Concrete

THMACO -- 3/4 inch

(19.0 mm)

Porous Asphalt Mix

PAM-9.5 -- 1.5 inch

(37.0 mm)

PAM-19.0 -- 3.0 inch

(75 mm)

Note 1 Application rate is based upon 110 pounds per square yard per inch (2.35 kilograms per square meter per millimeter) of thickness.

Note 2 SMA Intermediate design criterion allows the mixture to meet the definition of either nominal maximum aggregate size.

Note 3 Application rate for BM Type mixes should be determined from the actual specific gravity of the mixture as called for by the Materials Division or by region as indicated in Table 6.

SEC. 605.07 TYPICAL ASPHALT BASE MIX APPLICATION RATES

Table 6 should be used to determine the approximate quantity of base asphalt for construction and maintenance program projects. This table contains the average weight for the base mix based on the aggregate present in the District. If a location is not identified in Table 6, use 110 Lbs/S.Y./In.

Table 6 – Application Rates for Base Mix Asphalt

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Table 5 – Application Rates for Asphalt Base Mix

VIRGINIA DEPARTMENT OF TRANSPORTATION WEIGHT OF BASE ASPHALT MIXES FOR APPROXIMATE QUANTITY CALCULATIONS

DISTRICT AREAS Mass kg/m2/mm Lbs/S.Y./In

Bristol Abingdon-Marion-Wytheville-Galax 2.46 115 Bluefield-Big Stone Gap-Woodway-Bristol 2.39 112

Salem Buchanan-Roanoke-Salem-Radford-Martinsville

2.43 114

Lynchburg 2.41 113

Lynchburg Danville 2.35 110

South Boston 2.37 111

Richmond 2.35 110

Hampton Roads 2.35 110

Fredericksburg 2.35 110

Culpeper Charlottesville 2.52 118

Culpeper - Flint Hill 2.41 113

Staunton 2.39 112

NOVA Arlington - Fairfax 2.61 122

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SECTION 606 – PAVEMENT TYPE SELECTION PROCEDURES DETAILS


This document outlines VDOT’s Pavement Type Selection Procedures (PTSP) used in selecting the most functional and economical pavement type. These procedures are the results of the cooperation among various groups/divisions of VDOT and both asphalt and concrete industries. These PTSP are to be used with conventional Design Bid Build, Design Build, and Alternate Bidding contracts.

The procedures are aimed to provide the following:

1. Consistency

2. Conciseness

3. Transparency

4. Enhanced competition

5. Identical selection of pavement type by all qualified users upon following these procedures

SEC. 606.02 PAVEMENT TYPE SELECTION

The PTSP are a set of steps that lead to the determination of alternate structures using a variety of materials, pavement design, construction methodologies, and Life Cycle Cost Analysis (LCCA). Therefore, it is possible that more than one type of pavement (typically, asphalt and concrete) could be designed which is capable of accommodating the design traffic under the same environmental condition. However, the differing pavement types will have different cost and maintenance components as well as differing constructability issues. The pavement designer needs to select the type that best satisfies the interest of the Department and the traveling public by thoroughly assessing all the pertinent factors. Such process is called pavement type selection.

SEC. 606.03 PAVEMENT TYPES

Pavement Types

Pavement types are broadly categorized into the following:

• Flexible pavement o Asphalt pavement

• Rigid pavements o Jointed Plain Concrete Pavement (JPCP)

o Jointed Reinforced Concrete Pavement (JRCP)

o Continuously Reinforced Concrete Pavement (CRCP)

• Composite pavements (asphalt over concrete surface is typical in VA)

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SEC. 606.04 PAVEMENT DESIGN

Pavement design is the process of selecting a practical and economical combination of materials of known strength and adequate thicknesses to support anticipated traffic under the prevailing environmental conditions. Pavement will be designed following the appropriate procedures noted in this document.

SEC. 606.05 PAVEMENT TYPE SELECTION PROCEDURES (PTSP)

Typically, the following factors influence the selection of pavement types:

• Cost (both initial and future maintenance/rehabilitation)

• Geometry of the pavement to be built (if applicable)

• Geometry of the adjacent pavement (if applicable)

• Existing appurtenant features (median barriers, drainage structures, curb & gutters, lateral & overhead clearances, structures limiting the new or rehabilitated pavement structure)

• Maintenance of traffic

• Availability of local materials

• Maintaining or changing grade profile

• Corridor continuity

• Local experience The pavement type selection process is not an exact science as it involves not only engineering analysis but also subjective and complex consideration to project constraints which may or may not be agreed upon by all concerned. This is very important since it significantly impacts the Department’s budgetary and resource need. For typical projects, PTSP initiates at the project scope phase, which determines if the project will be a candidate for considering multiple pavement types. The process then involves the following components: design of alternatives, performing life cycle cost analysis, selection of pavement type, development of typical pavement section, signing/sealing of the selected pavement section, forwarding the typical section to the project manage and project advertisement. In general, the following four steps will be followed when selecting a pavement type for typical projects (alternate bid projects follow a slightly different process which is explained in Alternate Bidding Section of this document):

Step 1: Decide if multiple pavement types need to be considered

Step 2: Design different types of pavement

Step 3: Perform Life Cycle Cost Analysis (LCCA) on competing pavement types

Step 4: Select the pavement type

These steps are discussed in detail in the following sections.

Step 1: Decide if multiple pavement types need to be considered

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Two major categories are encountered in this step, namely: new alignment/reconstruction and rehabilitation projects. New alignment or reconstruction projects are generated from the six year plan, while the rehabilitation projects are initiated from the Maintenance Division’s pavement management process. While new alignment/reconstruction projects are prevailing examples, multiple pavement types could be considered for major rehabilitation projects as well. A general guideline for the criteria when multiple pavement types should be considered is provided below.

New Construction

New construction type projects could be sub-divided into the following two categories:

1. New Alignment:

Typically, brand new alignment projects are most suitable for considering multiple types of pavements. However, length and structure of the pavement are to be considered in deciding whether multiple pavement types provide realistic solutions. For example, pavement type for a new section that is too short could be simply decided by the pavement it is joining to. At the same time, multiple pavement types may not be realistic if the pavement structure is too thin. If the length of the project is at least 4 centerline miles or at least 16 lane miles and the design asphalt concrete thickness is at least 9 inches or design concrete pavement thickness is at least 8 inches then multiple pavement types will be considered for new alignment projects. This means if the designer starts with asphalt section and the section meets the above length criteria and the design asphalt thickness is at least 9 inches, then an equivalent concrete section needs will be considered and the steps described in this document will be followed to select the final pavement type. At the same time, if the designer starts with concrete section and the section meets the above length criteria and the design PCC thickness is at least 8 inches then an equivalent asphalt section will be considered. The steps described in this document will then be followed to select the final pavement type.

2. Reconstruction:

Reconstruction projects could involve either the same footprint or widening of an existing road and the following criteria are applied for selecting PTSP candidates.

a. For reconstruction along the same footprint projects, if the length of the project is at least 4 directional miles or at least 8 lane miles, and the design asphalt thickness is at least 9 inches or design concrete pavement thickness is at least 8 inches then multiple pavement types will be considered. The directional mile is used since reconstruction may often involve only one direction of a divided roadway.

b. For widening projects, if the length of the section is at least 4 miles and the existing asphalt thickness is at least 9 inches or the thickness of the existing PCC is at least 8 inches, multiple pavement types should be considered.

Major Rehabilitation

Certain types of major rehab projects may qualify for considering multiple pavement types. At a minimum, the rehabilitation solution should provide a design life of 20 years. In addition, if the length is at least 4 directional miles or at least 8 lane miles and the new design asphalt thickness is at least 9 inches or the new design pavement thickness (for PCC pavement) is at least 8 inches, multiple pavement types should be considered.

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The criteria and process described above are shown in Figure 1 with a detailed flowchart.

In situations where the above conditions are not met, pavement type is usually governed by adjacent or existing pavement or special needs. As a general guideline, following are some typical examples (not all inclusive) where multiple pavement types need not be considered:

1. Turning lane

2. Functional maintenance projects (for example, single lift Asphalt resurfacing projects)

3. Pavement preservation projects (for example, surface treatment, slurry seals etc.)

Step 2: Design different types of pavements

Once it is decided to consider multiple pavement types for the project and the possible alternate pavement types are identified, the appropriate pavements shall be designed following Chapter VI of Materials Division’s Manual of Instruction (MOI).

Step 3: Perform Life Cycle Cost Analysis (LCCA)

After designing the possible alternate pavement sections, Life Cycle Cost Analysis (LCCA) is to be performed to assess the economic worth of the alternate pavement sections. This consists of the initial cost estimate of the paving materials and the future maintenance activities necessary to maintain the road at an acceptable serviceability level to the traveling public. These activities include maintaining the pavement quality, namely smoothness and safety in terms of non-skidding, and the structural capacity, namely the elimination of cracks, faulting, potholes, and rutting. The present worth (PW) approach is generally used to represent the translation of specified amounts of costs or benefits occurring in different time periods into a single amount at present instant. However, Equivalent Uniform Annual Cost (EUAC) approach is used for certain major rehab projects where the design life between the competing options are not the same. • In PW approach, LCCA converts the initial and all expected maintenance/rehabilitation costs of the

differing pavement types into present worth values. In EUAC approach, the calculated PW is evenly distributed over the analysis period. For details on VDOT’s LCCA approach, please see the document titled “Guidelines for Life Cycle Cost Analysis” or Section 607 of Materials Division’s Manual of Instruction (Chapter VI).

Step 4: Select the final pavement type • If the present worth (or EUAC for certain major rehab projects) values in the LCCA for the competing

pavement type solutions differ more than 10%, the pavement type with the lowest present worth (or EUAC for certain major rehab projects) shall be recommended for final selection. When the net present worth (or EUAC for certain major rehab projects) for competing types of pavements is within 10%, other factors are examined as outlined in VDOT’s LCCA process (for non alternate bid projects) or the project is selected for alternate bidding (see the section on Alternate Bidding below for alternate bidding project selection criteria). If the project is not an alternate bid candidate, other factors that are not considered in the LCCA computation should be considered in conjunction with LCCA results. These factors along with the LCCA results are considered to make the final decision. These factors could be, but are not limited to:

• Initial project constructability

• Constructability of future improvements

• Volume of traffic

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• Maintenance of traffic

• Climate

• Recycling

• Adjacent existing pavement (if applicable)

• Traffic safety

• Incorporation of experimental features

• Participating local government preference

If any particular type of pavement is disregarded due to special circumstances despite the favorable LCCA result, documentation shall be provided in the pavement report by the pavement designer. The documentation shall include, but not be limited to, the type(s) of pavement not being considered and reasoning for exclusion. For projects that are selected for alternate bidding process, the final pavement type will be selected based on the outcome of the alternate bidding process.

SEC. 606.06 ALTERNATE BIDDING

Alternate bidding is the process where bids are solicited on two different pavement types for the same project. The final pavement type selection is based on the actual bid price of the project (not the pavement components only). Such practice, if applied to the right project, is expected to enhance competition within the contracting industry and potentially lead to lower costs for VDOT.

New construction and complete reconstruction projects meeting the criteria as described in Step 1 (and also outlined in Figure 1) are suitable candidates for the alternate bidding process. VDOT will perform LCCA on these projects based on the best estimates of the unit prices. If the difference between the PW for competing pavement types are within 10%, VDOT will pursue alternate bidding. Each alternate will be included in the bid package for solicitation. The final selection of the pavement type will be based on the least bid amount for the project. For Design Build projects, the final selection of the pavement type will follow the standard award process for Design Build projects.

It should be noted that alternate bidding may be considered for projects not meeting the above criteria but is deemed to provide opportunities for competition. Such decision will be made on case by case basis by the District. The Pavement designer shall document in the pavement report the pavement type alternative(s) and reasoning for inclusion in the project.

SEC. 606.07 HOW TO USE THE PROCEDURES

Pavement type selection procedures (PTSP) start at the scoping of any project. The scoping determines whether multiple pavement types are practical and the project is a candidate for PTSP. The procedures involve the following:

1. Start with the project scope and use the decision flow chart in Figure 1 to select the proper category

2. Follow the applicable procedures

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If a project is not a candidate for Pavement Type Selection Procedures (PTSP), the standard VDOT design process will be followed. This will involve detailed design of the selected pavement type, signing/sealing by the respective design engineer and forwarding the design to the respective project manager. On the other hand, if the project is a PTSP candidate, multiple pavement types will be considered and designed. Life Cycle Cost Analysis (LCCA) will be performed following VDOT’s LCCA process to assist in the determination of the final pavement type. The selected pavement design is signed and sealed by the respective design engineer and is ultimately forwarded to the project manager. If a project is selected for alternate bidding, the design engineer will sign and seal both pavement types and forward these two pavement designs to the project manager. Bids will be solicited on both these sections and the selection of the pavement type will be determined based on the least bid price of the project or following the standard award process for Design Build projects.

The pavement type selection process shall be performed under the purview of the respective District Materials Engineer. Prior to finalizing the pavement type selection, the pavement designer shall submit for review by Central Office Materials, the project details and pavement design recommendations for the following projects:

• All Interstates projects • All projects meeting the PTSP criteria

It is recommended that the District notify Central Office Materials early in the design process (for example, at the Preliminary Pavement Design Phase) to ensure review time will not adversely impact project scheduling. The preliminary pavement design (if any) will be sent to the CO Materials office after the activity 34P is established. Final pavement design report will be sent to the CO Materials as soon as the report is finalized.

The pavement design recommendations shall include, but not be limited to, all Pavement Design Software input and outputs, a copy of the Pavement Design Output and any noted exclusions or exceptions. Other projects not meeting this criterion may be submitted by the District for review by Central Office Materials.

Central Office will review the design for conformance with MOI requirements and provide a summary of comments to the District upon completion. The District Materials Engineer or District Materials Engineer designee will then finalize the pavement type, sign and seal the pavement design and forward it to the respective project manager for incorporation into the project plans and contract documents.

For projects where the alternate bid process is used, all alternates with the applicable plan sheets and other pertinent contract documents shall be included in the bid package. The final selection of the pavement type will be made after receiving bids. A flowchart summary of the process is shown in Figure 1.

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Figure 1: Pavement Type Selection Decision Work Flow

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SECTION 607 – LIFE CYCLE COST ANALYSIS

SEC. 607.01 EXECUTIVE SUMMARY

With increasing customer expectations and limited funding, VDOT must ensure that the most cost-effective, smooth, and long-lasting pavements are constructed on Virginia’s highways. With the volume of traffic using Virginia’s highways, the public will no longer tolerate excessive work-zone disruptions because of emergency or unplanned maintenance on a roadway. Additionally, VDOT cannot afford to rehabilitate these pavements prematurely. Both the public and VDOT want VDOT to “Get In, Get Out, and Stay Out.” To fulfill this expectation, VDOT is designing pavements using new approaches and enhanced state-of-the-art materials.

VDOT like many other agencies utilizes life cycle cost analysis (LCCA) procedure into the process of selecting pavement type. This analysis incorporates proven national methodologies customized to Virginia’s unique circumstances. VDOT looks beyond initial construction costs by considering the future maintenance and rehabilitation needs associated with a particular type of pavement. This approach, then, improves the decision-making process by enabling the selection of the most cost-effective type of pavement based on an estimation of costs incurred throughout a suitable analysis period, or “life cycle.” For the LCCA procedure, a 50-year analysis period is considered sufficiently long to capture the maintenance and rehabilitation costs that span at least one full series of treatment activities with the exception of major rehab type projects where the analysis period is taken as the design life for the competing pavement options.

The procedure herein was derived largely from the Federal Highway Administration Technical Bulletin, Life Cycle Cost Analysis in Pavement Design, discussion with various stakeholders and both asphalt and concrete industries. Geared toward state highway agency personnel responsible for designing highway pavements, the FHWA bulletin provides technical guidance and recommendations on “good practice” in conducting LCCA in pavement design. It was authored by representatives of various state transportation departments, the Federal Highway Administration (FHWA), the National Asphalt Pavement Association, and the American Concrete Pavement Association. Additionally, VDOT’s LCCA Guidelines draw upon the experience and expertise of its own workforce, particularly in areas related to pavement performance prediction and maintenance effectiveness as well as practices by other agencies. Where records are available, historic performance data were used to support planned maintenance/rehabilitation intervals for certain activities.

LCCA will enhance VDOT’s ability to make sound engineering and cost-effective economic decisions pertaining to the construction/reconstruction and major rehabilitations of Virginia’s major highways. However, it is important to remember that the LCCA process is based on the premise that the pavements are properly designed and will be reasonably maintained, that the quality of the construction and materials is consistently

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good, and that the pavement is not subject to adverse or unforeseen site conditions. Performance of the different pavement types and extent of specific rehabilitation treatment had been established based on available performance data, local practice and engineering judgments. Actual performance and the exact extent of the specific rehabilitation treatment of a particular project could be different. However, established parameters reflect the best possible realistic and practical assumptions that are needed to be made to perform LCCA computations.

Sec. 607.02 Introduction A major factor in selecting the type of pavement for use on new construction and major rehabilitation projects is cost. In many cases, the initial construction cost is the main consideration. Although a particular pavement type may have a low initial cost, the future maintenance and rehabilitation costs may be exorbitant and, therefore, must be considered in a fair and objective decision-making process. In order to account for the initial and future costs associated with the construction and maintenance of roadway infrastructure, a life cycle cost analysis (LCCA) should be performed. LCCA may not be necessary on all projects largely because of the nature and location of a particular project. LCCA is necessary for projects where multiple pavement types are feasible and considered. Materials Division’s “Pavement Type Selection Procedures” document (section 606 of Chapter VI of MOI) outlines the situations where multiple pavement types will be considered and hence LCCA needs to be performed in order to select the most cost effective option.

Purpose

The purpose of this document is to provide technical guidance to VDOT engineers involved in selecting a pavement type for major construction and rehabilitation projects that provides the best cost effective solution. Separate tables have been generated and presented herein outlining the assumed performance and rehabilitation year and treatment for separate pavement type.

What is LCCA?

LCCA is an economic method to compare alternatives that satisfy a need in order to determine the lowest cost alternative. According to Chapter 3 of the AASHTO Guide for Design of Pavement Structures, life cycle costs “refer to all costs which are involved in the provision of a pavement during its complete life cycle.” These costs borne by the agency include the costs associated with initial construction and future maintenance and rehabilitation. Additionally, costs are borne by the traveling public and overall economy in terms of user delay. The life cycle starts when the project is initiated and opened to traffic and ends when the initial pavement structure is no longer serviceable and reconstruction is necessary.

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History of LCCA in VDOT

VDOT has used LCCA to evaluate and select pavement types on new Interstate and Primary Route projects for many years. Past LCCAs for pavements considered a 24-foot surface width and dealt with the cost for a lane mile. A 30-year analysis period was used, and only continuously reinforced concrete, jointed concrete, and flexible pavements were considered. In 2002, VDOT’s LCCA was revised. One of the major changes was incorporation of 50 year analysis period and inclusion of the entire project cost as opposed to lane mile cost. The current revision (in 2011) reflects the updated performance of some materials and treatment, elimination of salvage value and inclusion of select major rehabilitation projects for LCCA process.

SEC. 607.03 ECONOMIC ANALYSIS COMPONENTS

Analysis Period

To maintain consistency with the FHWA Technical Bulletin, Life Cycle Cost Analysis in Pavement Design, LCCA periods should be sufficiently long to reflect long-term differences associated with reasonable maintenance strategies. The analysis period should generally be longer than the pavement design period. As a rule of thumb, the analysis period should be long enough to incorporate at least one complete cycle of rehabilitation activity. The FHWA’s September 1996 Final LCCA Policy Statement recommends an analysis period of at least 35 years for all pavement projects, including new or total reconstruction projects and rehabilitation, restoration, and resurfacing projects. For VDOT’s LCCA procedure, a 50-year analysis period was selected for new construction and reconstruction type projects. This period is sufficiently long to reflect the service lives of several rehabilitation activities. For major rehab type projects where multiple pavement types are considered and LCCA is required, the analysis period is taken to be the design life of the rehab design.

Discount Rate

In order to account for the cost related to future activities, the time value of money must be considered. In LCCA, the discount rate is used. The discount rate is defined as the difference between interest and inflation rates. Historically, this value has ranged from 2% to 5%; for LCCA purposes, a value of 4% will be used. This value is consistent with the values recommended in the FHWA Interim Technical Bulletin and practices by many other state agencies. The discount rate accounts not only for the increased cost associated with performing an activity in the future but also for the economic benefit the agency would receive if those funds were instead invested in an interest-bearing account.

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Evaluation Methods

Numerous economic analysis methods can be used to evaluate pavement alternatives. The two most common are the present worth (PW) method and the equivalent uniform annual cost (EUAC) method.

The EUAC method describes the average cost an agency will pay per year over the analysis period. All costs including initial construction and future maintenance are distributed evenly. Although this dollar value may not seem realistic in years when little pavement action is required, it can be used to evaluate and compare alternatives.

The PW method reports initial and future pavement costs as a lump sum amount in today’s dollar value. For activities that occur in the initial year of the analysis period, the PW cost is the same as the actual cost, i.e., no adjustment for inflation and interest. For future maintenance and rehabilitation activities, the PW cost is less than the actual cost (based on today’s unit prices) since total costs are discounted. Please note that for two identical actions that occur 30 years apart, the later action will cost much less. This is because of the number of years that are discounted. The PW method is the more widely used approach for pavement LCCA. It gives an indication of how much a pavement alternative will cost over the analysis period and can be used to clearly compare alternatives for lowest cost. The formula to compute both PW and EUAC are provided below.

PW = Initial cost + ∑=

n

kkhabCost

1

Re * ( )

+ ni11

Where: i = discount rate

k = year of activity

n = analysis period

EUAC = PW * ( )( )

−++

111

n

n

iii

Where: i = discount rate

n = analysis period

Sensitivity Analysis

As with any analysis, it is important to understand what variables make the largest difference in the final results. For pavement design, the pavement subgrade strength and

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traffic loading have the largest impact on the design outcome. For LCCA, multiple variables can affect the final PW or EUAC for a pavement alternative. For example, the unit cost of a material alone can be significant enough to cause a particular alternative go from the lowest PW to the highest. Therefore, the engineer must ensure that the unit costs used are reasonable; likewise, it is important to understand how sensitive the cost of an alternative is to the input assumptions. This is accomplished by performing a limited sensitivity analysis whereby various combinations of inputs are selected to qualify their effect on the analysis results. Other factors that can influence the LCCA results are analysis period, and timing of activities.

SEC. 607.04 COST FACTORS

Numerous costs are included in LCCA for pavements, ranging from initial costs associated with new construction to future maintenance costs associated with patching, sealing, and other activities.

Initial Costs

To conduct an LCCA for comparing pavement alternatives, the initial cost is a major percentage of the PW or EUAC over the analysis period. The initial cost is determined at Year 0 of the analysis period.

Although numerous activities are performed during the construction, reconstruction, or major rehabilitation of a pavement, only those activities that are specific to a pavement alternative will be included in the initial costs. By focusing on those activities, the engineer can concentrate on estimating the quantities and costs related to those activities. Actions dependent on pavement type include, but are not limited to the following:

• Milling

• Pavement Removal

• Asphalt Concrete Paving

• Portland Cement Concrete Paving

• Fracturing Portland Cement Concrete Slabs

Rehabilitation Costs

For all pavement options, the initial pavement life is designed to support traffic for 30 years. At around the end of the 30-year period, the pavement must be rehabilitated. For flexible pavements, this rehabilitation generally includes removing AC surface and intermediate materials and replacing with new AC material. For rigid pavements, concrete pavement restoration (CPR) is generally conducted and an AC overlay may be placed. However, wherever feasible, concrete overlays could also be considered on both asphalt

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and concrete pavements. Rehabilitation activities may include but are not limited to the following:

• Milling

• AC paving

• PCC and AC patching

• Joint cleaning

Structural/Functional Improvement Costs

Structural/functional improvement activities are performed during the life of a pavement in order to maintain a smooth, safe, durable pavement surface. Structural/functional improvements are designed to last 10 years (higher life for SMA mixes). Typical improvement activities include the following:

• Milling

• AC and PCC patching

• AC paving

• PCC grinding

• Joint cleaning and sealing

Maintenance Costs

All pavement types require preventive and corrective maintenance during their service life. The timing and extent of these activities vary from year to year. Routine reactive type maintenance cost data are normally not available except on a very general, area wide type cost per lane mile. Fortunately, routine reactive type maintenance costs are generally not very high due to the relatively high performance levels maintained on major highway facilities. Further, state highway agencies that do report routine reactive maintenance costs note little difference between most alternative pavement strategies. When discounted to the present, small reactive maintenance cost differences have negligible effect on PW and can generally be ignored. Therefore, they are not included in this LCCA procedure.

Salvage Value

At the end of the LCCA period, the pavement structure may be defined as having some remaining value to the managing agency, known as the salvage value. Different pavement types attain different condition at the end of the analysis period. If the condition of the pavement at the end of the analysis period is such that a complete removal and replacement is warranted, then the salvage value would have been the cost of any residual materials

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obtained from the pavement system (materialized by the agency). However, in most situations and depending on the timing and extent of the last maintenance treatment, the pavement either continues to remain in service or some kind of rehabilitation treatment is performed on the existing pavement (which may involve partial removal of the pavement materials or reclamation type treatment combined with overlays). So, pavements typically offer some sort of remaining life at the end of analysis period. In such cases, the residual value of the materials are not realized. Therefore, the remaining life essentially represents the salvage value of the pavement for practical purpose. Estimating a dollar figure for this component could be complex. Fortunately, the dollar figures for the ‘salvage value’ for the competing pavement types when discounted 50 years to PW are not expected to be significantly different. For simplicity, VDOT disregards the salvage value for the competing pavement types in its LCCA process.

SEC. 607.05 OVERVIEW OF LCCA PAVEMENT OPTIONS

In order to conduct a LCCA, different pavement options must be identified and compared for a project. The number and type of viable pavement options depend on the project’s characteristics. After an examination of the pavement structures (flexible, rigid, and composite), six pavement options were created. The following table identifies these pavement options:

Construction/Major Rehabilitation Pavement Options

Asphalt Concrete Construction/Reconstruction

Jointed Plain Concrete Construction/Reconstruction with Tied PCC Shoulders

Jointed Plain Concrete Construction/Reconstruction with Wide Lane and AC Shoulders

Continuously Reinforced Concrete Pavement Construction/

Reconstruction with Tied PCC Shoulders

Continuously Reinforced Concrete Pavement Construction/

Reconstruction with Wide Lane and AC Shoulders

Major Rehabilitation

The pavement options, criteria and suppositions in the table were made to accommodate the consistent application of LCCA across the state. Without these guidelines, an infinite number of pavement options could be developed. For some pavement options, specific criteria and suppositions were made. The general criteria and suppositions made are

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summarized below. It should be noted that the actual rehabilitation treatment on a particular pavement may be different from these assumptions. The assumptions made in this LCCA document reflect the prevailing VDOT practice and does not necessarily put a binding requirement on the pavement designers while rehabilitating pavements. For example, unbonded or bonded PCC overlay could be considered to rehab a PCC section if such treatment provides the best solution to the specific circumstance even though it is not programmed in the LCCA process for PCC pavements.

The general criteria and suppositions made are:

• No reconstruction is planned during the analysis period beyond the original rehabilitation/reconstruction.

• Flexible pavements remain flexible throughout the analysis period, i.e., no white-topping.

• Rigid pavements are overlaid with AC during the analysis period. No unbonded or bonded concrete overlays are programmed.

• Subsurface drainage systems are independent of pavement type. If a site needs drainage, then all options call for drainage. Therefore, this cost is treated as fixed regardless of pavement type.

• Full-depth shoulders are designed to carry potential future traffic.

• The timing of functional improvements and major rehabilitation is fixed.

• The activities associated with new construction, reconstruction, major rehabilitation, and functional/structural improvements are a function of the project. The activities included in LCCA must be determined by the engineer and supported by documentation.

Reconstruction is defined as the treatment that involves removal (partial or full depth) and/or manipulation of unbound materials for asphalt pavement. Removal and replacement of the concrete pavement (with or without manipulation of unbound materials) are considered reconstruction. Unbonded concrete overlays are considered reconstruction. Bonded concrete pavement is designed to improve structural capacity of the existing pavement and is not considered as reconstruction.

SEC. 607.06 ASPHALT PAVEMENT CONSTRUCTION/RECONSTRUCTION

For most projects, asphalt pavement construction or reconstruction is a viable option. Asphalt pavement can be constructed on a new alignment or an existing alignment. For existing alignments, the in-situ pavement is removed completely. Asphalt pavement could be utilized to rehabilitate existing PCC pavement through fracturing the PCC pavement and overlaying with AC layers. Fracturing techniques includes break and seat, crack and

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seat, and rubblization. The type of fracturing performed is based on the existing rigid pavement type, e.g., jointed plain, jointed reinforced, or continuously reinforced concrete. Once the pavement has been fractured and overlaid, it is considered a flexible pavement structure. Such an option is considered to behave like a new asphalt structure and follow the same life cycle as new AC pavement.

Beginning early 2000, VDOT starts utilizing a premium asphalt mix known as Stone Matrix Asphalt or SMA. This mix provides better performance compared to conventional asphalt mixes. In order to differentiate between the performance of SMA and conventional mixes, two separate performance tables had been generated and presented in this section. The designer needs to use appropriate performance table based on the asphalt mixes to be used in the pavement section.

Performance for Dense Graded Mixes

As with all pavement options, several criteria were established and assumptions made:

1. The initial pavement design life is 30 years. Because of functional mill and replace at Year 12 and 22, major rehabilitation is not scheduled until Year 32.

2. For the structural rehabilitation at Year 32, the pavement surface life is 12 years.

Functional mill and replace is a fixed activity at Years 12, 22, and 44 in order to provide 10 additional years of life to the pavement surface and structure. The 10-year period is the average life for an AC surface based on data in VDOT’s pavement management database.

For structural adequacy, the pavement overlay design life at Year 32 is 20 years. Pavement activities and required structures must be determined by the engineer (e.g., thickness of AC base, intermediate and surface layers) at the time of rehab.

Patching of AC pavements is based on area of pavement surface.

Preventive maintenance activities considered in the analysis include surface treatments (e.g., BSTs, thin overlays, slurrys, microsurfacing), crack sealing, and patching. Preventative maintenance is only specified in the analysis for the shoulders if a functional or structural improvement is performed on the mainline pavement. No preventative maintenance is programmed for the mainline pavement as part of the LCCA.

Pavement Activities Table Year 0 – New Construction/Reconstruction Year 12 – Functional Mill and Replace

Mainline*

AC Surface Material

AC Intermediate Material

Mainline Pre-overlay repair - Patch – 1% (up to the top of base layer)

Mill – Surface Layer

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Year 0 – New Construction/Reconstruction Year 12 – Functional Mill and Replace

AC Base Material

Stabilized Drainage Layer

CTA or DGA Subbase

Shoulders*

AC Surface Material


AC Base Material


CTA or DGA Subbase

Replace with AC Wearing Course – one layer

Shoulders Surface Treatment

*As appropriate

Year 22 – Functional Mill and Replace Year 32 – Major Rehabilitation

Mainline Pre-overlay Repair - Patch – 1% (up to the top of base layer)

Mill – Surface layer

Replace with AC Surface Materials – one layer


Mainline Pre-overlay Repair - Patch – 5% (full depth)

Deep Mill (All Surface and Intermediate Layers)

Replace with

AC Base Material


AC Wearing Course

Shoulders Overlay with AC Wearing Course

Year 44 – Functional Mill and Replace Year 50 – Salvage Value


Mill - Surface layer

Replace with AC Wearing Course - one layer

None

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Performance for SMA surface

The designer will consider this section if the pavement is to be built using SMA mixes. As with all pavement options, several criteria were established and assumptions made. It is assumed that the pavement system receives appropriate SMA mixes during all maintenance treatments.

1. The initial pavement design life is 30 years. The pavement system will undergo a functional mill and replace at Year 15 and major rehabilitation is scheduled at Year 28.

2. For the structural rehabilitation at Year 28, the pavement surface life is 15 years (assuming SMA mixes to be used).

3. Functional mill and replace is a fixed activity at Years 15 and 43 in order to provide 13 additional years of life to the pavement surface and structure.

4. For structural adequacy, the pavement overlay design life at Year 28 is 20 years. Pavement activities and required structures must be determined by the engineer (e.g., thickness of AC base, intermediate and surface layers) at the time of the rehab.

5. Patching of AC pavements is based on area of pavement surface.

6. Preventive maintenance activities considered in the analysis include surface treatments (e.g., BSTs, thin overlays, slurrys, microsurfacing), crack sealing, and patching. Preventative maintenance is only specified in the analysis for the shoulders if a functional or structural improvement is performed on the mainline pavement. No preventative maintenance is programmed for the mainline pavement as part of the LCCA.

Pavement Activities Table Year 0 – New Construction/Reconstruction Year 15 – Functional Mill and Replace

Mainline*

AC Surface Material


AC Base Material




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Year 0 – New Construction/Reconstruction Year 15 – Functional Mill and Replace


CTA or DGA Subbase

Shoulders*

AC Surface Material


AC Base Material


CTA or DGA Subbase


*As appropriate

Year 28 – Major Rehabilitation Year 43 – Functional mill and replace

Mainline Pre-overlay Repair - Patch – 5% (full depth)

Deep Mill (All Surface and Intermediate Layers)

Replace with

AC Base Material


AC Wearing Course

Shoulders Overlay with AC Wearing Course





Year 50 – Salvage Value

None

SEC. 607.07 JOINTED CONCRETE PAVEMENT

CONSTRUCTION/RECONSTRUCTION WITH TIED PORTLAND CEMENT

CONCRETE SHOULDERS

For most projects, a jointed concrete pavement with tied PCC shoulders is a viable construction or reconstruction option. Jointed concrete pavement can be constructed on a

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new alignment or on an existing alignment. If the existing pavement on an alignment is flexible, then the jointed concrete pavement can be constructed on top of it (if geometrically feasible). At the same time, unbonded jointed concrete pavement can be constructed on top of existing asphalt or concrete pavement. Such a treatment is typically comparable with reconstruction. Such pavement will follow the same maintenance cycles as that of a new jointed concrete pavement.


1. Initial pavement design life is 30 years.

2. For structural adequacy, the pavement overlay design life at Year 30 is 20 years. Pavement activities and structures must be determined by the engineer (e.g., thickness of AC base, intermediate and surface layers).

3. The mill and replace is a fixed activity at Year 42 or at Year 45 (if SMA mix is utilized) in order to provide 10 or 13 (for SMA mixes) additional years of life to the pavement surface and structure.

4. The full-depth patching percentage for composite pavement is based on the pavement surface area.

5. The full-depth patching percentage for jointed concrete pavement is based on the pavement surface area.

6. PCC slab costs include the costs of tie bars, dowels, cut joints, and seal joints.

Pavement Activities Table Year 0 - New Construction/Reconstruction Year 10 – Concrete Pavement Maintenance

Mainline*

Pavement Removal (Reconstruction)

PCC Slab


CTA or DGA Subbase Shoulders*

Shoulder Removal (Reconstruction)

PCC Slab


CTA or DGA Subbase

Soil Stabilization

Mainline Patching – 1.5% (of surface area)

Clean and Seal Joint – 100%

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Year 20 – Concrete Pavement Restoration Year 30 – Concrete Pavement Restoration and AC Overlay

Mainline (Concrete Pavement Repair)

Patching – 5% (of surface area)

Clean and Seal Joints – 100%

Grinding – 100%

Mainline Pre-overlay Repair: Patch – 5% (of surface area)

AC Overlay (Minimum two lifts) with:

AC Surface Material


AC Base Material

Shoulders AC Overlay (Minimum two lifts) with:

AC Wearing Course


AC Base Material

Year 42 or 45* –Mill and Replace Year 50 – Salvage Value

Mainline Pre-overlay Repair

Patching (AC overlay) - 2.5% (of surface area)

Patching (PCC Base) – 2.5% (of surface area)

Mill – Surface layer

Replace with AC Intermediate Materials – one layer

Overlay with AC Wearing Course – one layer

Shoulders Overlay with AC Wearing Course – one layer

None

*If SMA mixes utilized at year 30

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SEC. 607.08 JOINTED PLAIN CONCRETE PAVEMENT

CONSTRUCTION/RECONSTRUCTION WITH WIDE LANE (14 FEET) AND

ASPHALT CONCRETE SHOULDERS

For most projects, a jointed concrete pavement with wide lanes and AC shoulders is a viable construction or reconstruction option. Jointed concrete pavement can be constructed on a new alignment or an existing alignment. If the existing pavement on an alignment is flexible, then the jointed concrete pavement can be constructed on top of it (if geometrically feasible). At the same time, unbonded jointed concrete pavement can be constructed on top of existing asphalt or concrete pavement. Such a treatment is typically comparable with reconstruction. Such pavement will follow the same maintenance cycles as that of a new jointed concrete pavement.


1. The initial pavement design life is 30 years for the mainline. For the AC shoulders, the total thickness of the AC layers will be equal to the thickness of the mainline PCC slab.


3. The mill and replace is a fixed activity at Year 42 or at Year 45 (if SMA mixes are utilized) in order to provide 10 or 13 (for SMA mixes) additional years of life to the pavement surface and structure.

4. The full-depth patching percentage for composite pavement is based on the pavement surface area.

5. The full-depth patching percentage for jointed concrete pavement is based on the pavement surface area.

6. PCC slab costs include the costs of tie bars, dowels, cut joints, and seal joints.


Mainline with 14-Foot Lanes* – Inside and Outside

Mainline Removal (Reconstruction)

PCC Slab


Mainline Patching – 1.5% (of surface area)


Shoulders

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Year 0 - New Construction/Reconstruction Year 10 – Concrete Pavement Maintenance

CTA or DGA Subbase

Shoulders*


AC Surface Material


AC Base Material

CTA or DGA Subbase

Soil Stabilization

Surface Treatment

*As appropriate





Grinding – 100%


Mainline Pre-overlay Repair: Patch – 5% (of surface area)

AC Overlay (Minimum two lifts) with:

AC Surface Material


AC Base Material

Shoulders AC Overlay (Minimum two lifts) with:

AC Wearing Course


AC Base Material

Year 42 or 45*– Mill and Replace Year 50 – Salvage Value


Patching (AC overlay) - 2.5% (of surface area)

Patching (PCC Base) – 2.5% (of surface area)

None

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Mill – Surface Course

Replace with AC Intermediate Materials – one layer

Overlay with AC Wearing Course – one layer

Shoulders Overlay with AC Wearing Course – one layer


SEC. 607.09 CONTINUOUSLY REINFORCED CONCRETE PAVEMENT

CONSTRUCTION/RECONSTRUCTION WITH TIED PORTLAND CEMENT

CONCRETE SHOULDERS

Continuously reinforced concrete pavement with tied PCC shoulders is a viable construction or reconstruction option. Continuously reinforced concrete pavement can be constructed on a new alignment or an existing alignment. If the existing pavement on an alignment is flexible, then the continuously reinforced concrete pavement can be constructed on top of it (if geometrically feasible).





4. The full-depth patching percentage for composite pavement is based on pavement surface area.

5. The full-depth patching percentage for continuously reinforced concrete pavement is based on surface area.


Mainline*

Mainline Removal (Reconstruction) Mainline Patching – 1% (of surface area)

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January 2018

Year 0 - New Construction/Reconstruction Year 10 – Concrete Pavement Maintenance

PCC Slab


CTA or DGA Subbase

Shoulders*


PCC Slab


CTA or DGA Subbase

Soil Stabilization

Clean and Seal Longitudinal Joint – 100%

*As appropriate





Grinding – 100%

Mainline Concrete Pavement Restoration: Patching – 5% (of surface area)

AC Overlay with (typically two lifts):

AC Wearing Course

AC Intermediate or Base Material

Shoulders AC Overlay (typically two lifts) with:

AC Wearing Course


Year 42 or 45* –Mill and Replace Year 50 – Salvage Value

Mainline Patching (AC Overlay) – 2.5%

None

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Patching (PCC Base) – 2.5%

Mill - Surface Course

Replace with AC Wearing Course – one layer



SEC. 607.10 CONTINUOUSLY REINFORCED CONCRETE PAVEMENT

CONSTRUCTION/RECONSTRUCTION WITH WIDE LANES (14 FEET) AND

AC SHOULDERS

Continuously reinforced concrete pavement with wide lanes and AC shoulders is a viable construction or reconstruction option. Continuously reinforced concrete pavement can be constructed on a new alignment or an existing alignment regardless of the existing pavement type. If the existing pavement on an alignment is flexible, then the continuously reinforced concrete pavement can be constructed on top of it (if geometrically feasible).





4. The full-depth patching percentage for composite pavement is based on pavement surface area.

5. The full-depth patching percentage for continuously reinforced concrete pavement is based on surface area.

Pavement Activities Table Year 0 – New Construction/Reconstruction Year 10 – Concrete Pavement Maintenance

Mainline with 14-Foot Lanes* – Outside and Inside

Mainline

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Pavement Removal (Reconstruction)

PCC Slab


CTA or DGA Base

Shoulders*


AC Surface Material


AC Base Material

CTA or DGA Subbase

Soil Stabilization



Shoulders

Surface Treatment



Patching – 5%

Clean and Seal Joints – 100% Grinding – 100%


Mainline Concrete Pavement Restoration: Patching – 5%

AC Overlay (typically two lifts) with: AC Wearing Course


Shoulders AC Overlay (typically two lifts) with:

AC Wearing Course


*As appropriate

Year 42 or 45* – Mill and Replace Year 50 – Salvage Value


None

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January 2018

Patching (AC Overlay) - 2.5%

Patching (PCC Base) – 2.5%

Mill - Surface course

Replace with AC Surface Course – one layer


*For SMA mixes

SEC. 607.11 LCCA FOR MAJOR REHABILITATION PROJECTS

As stated in the Pavement Type Selection Procedures document (also Section 606 of Chapter VI of the MOI), multiple pavement types will be considered for major rehabilitation projects that meet certain length and structural criteria as described in that document. The rehabilitation design life for such projects must be at least 20 year. Pavement at this stage is significantly old and projection of service life for another 50 years is not realistic. For performing LCCA on major rehab projects, analysis period will be considered same as design life. The maintenance activity will be the same as those for the respective surface type up to the design life (not including any treatment necessary at the end of design life). For example, if the design life for major rehabilitation project is 20 years, the analysis period will also be 20 years. For AC option, overlay activities will be considered at year 15 (SMA mixes) and 12 (Superpave mixes). For PCC surface, concrete pavement maintenance will be conducted at year 10. However, CPR activity scheduled at year 20 will not be considered for LCCA since 20 year marks the end of analysis period in this case. If the design life for the competing options are different, Equivalent Uniform Annual Cost (EUAC) approach shall be used instead of Present Worth (PW) approach to accommodate the difference in design life. EUAC distributes the PW of the each option (initial cost plus any treatment cost during the design life) equally over the analysis period. The formula to compute both PW and EUAC are provided in section II of this document.

SEC. 607.12 UNIT COSTS AND MEASURES

The life cycle cost for a pavement option is dependent on the corresponding activities required to construct and maintain the pavement. The cost for each activity is a function of unit cost and quantity measure. The following table provides units of measure. The measure is based on the Measurement and Payment Section in VDOT’s Road and Bridge Specifications for each activity. The unit cost is based on historical and current costs to VDOT for similar or equivalent measures (i.e., quantities).

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Activity Measure

Milling/Planing Square Yard – Inch

Fracturing PCC Square Yard

AC Surface Material/Wearing Course Tons

AC Intermediate Material Tons

AC Base Material Tons

Cold Central Plant Recycling Material (CCPRM) Tons

Stabilized Drainage Layer Tons

Pavement Demolition and Removal – Existing AC Square Yard

Pavement Demolition and Removal – Existing PCC Square Yard

Aggregate Subbase Cubic Yard or Ton

Cement Treated Aggregate Tons

Full Depth Reclamation (FDR) Square Yard

Patching – CRCP Square Yard

Patching – JPCP Square Yard

Patching – AC Tons

PCC Grinding Square Yard

Joint Cleaning and Sealing Linear Foot

CRCP Square Yard

JPCP Square Yard

Surface Treatment Depends on Material Selected

SEC. 607.13 INTERPRETATION OF RESULTS

Once the LCCA is completed for a project, the PW cost results must be interpreted. For new construction (new alignment and reconstruction) projects, if the PW values differ by more than 10 percent, the pavement type with the lowest present worth shall be recommended for final selection. If the PW values are within 10 percent, the project is a suitable candidate for alternate bidding process and the final selection of the pavement type will be made based on the bids received on two different pavement types.

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For major rehab projects, if the PW values (or EUAC if applicable) differ by more than 10 percent, the pavement type with the lowest present worth shall be recommended for final selection. However, ancillary costs (like maintenance of traffic, guard rail etc.) will be taken into consideration before making the final selection. If the PW values (or EUAC if applicable) are within 10 percent, the Pavement designer will consider all pavement options as economically feasible. If more than one pavement option is determined to be economically feasible, then factors such as the following must be considered before making the final selection.

• INITIAL CONSTRUCTIBILITY

• CONSTRUCTIBILITY OF FUTURE IMPROVEMENTS

• VOLUME OF TRAFFIC

• MINTENANCE OF TRAFFIC

• CLIMATE

• RECYCLING

• ADJACENT EXISTING PAVEMENT (IF APPOLICABLE)

• TRAFFIC SAFETY

• INCORPORATION OF EXPERIMENTAL FEATURE

• PARTICIPATING LOCAL GOVERNMENT PREFERENCE

SECTION 608 – PROJECT SELECTION GUIDELINES FOR COLD PAVEMENT

RECYCLING

SEC. 608.01 PURPOSES AND GOAL

The guidelines provided herein are intended to aid the user in properly selecting candidate projects when rehabilitating flexible or composite pavements using Cold Pavement Recycling. Cold Pavement Recycling consists of three processes -Cold In-Place Recycling (CIR), Cold Central Plant Recycling (CCPR), and Full-Depth Reclamation (FDR).

The goal of selecting the appropriate pavement recycling approach is to provide adequate pavement structural capacity to meet the projected traffic over the design life with consideration to the depth of the deteriorating layers, economics, and the time needed to complete the project.

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January 2018

SEC. 608.02 DEFINITIONS

The CIR, CCPR, and FDR processes are defined below (paraphrased from ARRA’s Basic Asphalt Recycling Manual and Wirtgen’s Cold Recycling Manual):

CIR is a process in which a portion of the asphalt pavement layers are pulverized, stabilized, and repaved in place. This is most commonly performed using emulsified asphalt or foamed asphalt as the stabilizing agents and is usually performed at a depth of 3 to 6 inches. The pavement may be milled, stabilized, and repaved using the same machine or machine train or paved from stabilized, windrowed material using traditional practices.

CCPR is similar to CIR but the stabilizing operation occurs at a mobile or central plant location. For rehabilitation projects, the asphalt materials are milled, processed at a mobile or central plant location and then repaved using traditional practices. CCPR is used as a base layer in pavement rehabilitation on the same project. Typical layer thicknesses range from 3 to 6 inches; however, multiple lifts may be placed.

FDR is a process in which the bound layers and a predetermined portion of the unbound aggregate materials are pulverized, stabilized, and compacted in place. Common stabilizing additives include: hydraulic cement, lime, fly ash, cement kiln dust, lime kiln dust, emulsified asphalt, foamed asphalt, or some combination of these materials. Treatment depths generally range between 6 to 12 inches but vary depending on the thickness of the existing pavement structure.

SEC. 608.03 SELECTION OF REHABILITATION/CONSTRUCTION PROJECTS

Cold pavement recycling applies to rehabilitating in service pavement. However, CCPR materials can be used on new construction projects as a bound flexible base material following the guidelines provided in this document. Also, CCPR materials shall not be used as the final riding surface.

(a) Initial Project Selection Criteria

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January 2018

For rehab projects, appropriate pavement recycling candidate projects should be identified by first obtaining the following information:

1. Distress Rating Data - Projects identified as Restorative Maintenance (RM) or Reconstruction (RC) as defined in VDOT’s Maintenance Division “Supporting Document for the Development and Enhancement of the Pavement Maintenance Decision Matrices” are typically suitable candidates. Furthermore, depending on circumstances, projects identified under other Maintenance Activity Categories may be suitable recycling candidates.

2. Project Length – The total project length should be greater than approximately 5 lane miles for CIR or greater than approximately 3 lane miles for FDR. The total project length can be any size for CCPR projects.

3. Maintenance History - A substantial rehabilitation effort may be needed if existing or projected patching exceeds approximately 15% of the pavement surface area or if applied overlays did not achieve their expected service life.

4. Pavement Management System (PMS) History - The PMS can be used to obtain the total bound and unbound layer thickness, the layers material composition, and the Critical Condition Index (CCI) values with respect to time.

(b) Project-Level Pavement Forensic Investigation

It is essential to conduct a project level field forensic investigation to identify the failure mechanism on the project. The Materials Division Manual of Instructions, Section 600 discusses the required elements of a project-level pavement forensic investigation. Additionally, the use of ground-penetrating radar (GPR) is strongly recommended to determine layer thicknesses and identify changes in pavement structure.

If FDR is considered, soil borings are required unless waived by the Engineer to classify the aggregate base and subgrade materials (USCS Soil Classification). The results of the classification tests shall be used to determine the choice of stabilizing agent(s). Generally, cohesive materials should be stabilized using lime. Non-cohesive materials may be stabilized with cementitious or bituminous stabilizing agents (with cementitious stabilizing agents being preferred for silty materials).

(c) Project-Level Recycling Considerations

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January 2018

FDR is intended to correct pavement deterioration due to failures in the subgrade or unbound base /subbase layers for flexible pavement structures. A layer coefficient value for FDR of 0.25 shall be used for design purposes.

CIR is intended to correct pavement deterioration within the bound layers of a flexible pavement or the asphalt layers of a composite pavement. CIR is typically performed at 3 to 6 inch depth. A layer 4 coefficient value for CIR of 0.35 shall be used for design purposes. When the pavement deterioration is located within approximately 3 inches of the surface, CIR may not be as cost effective as a typical mill and overlay. When pavement deterioration is located within approximately the bottom two inches of thick bound layers, CIR is usually not a good candidate as the existing pavement structure may not be able to support the weight of the construction equipment. In these cases, FDR should be considered to stabilize this area in place. .

(d) Consideration for using CCPR materials

CCPR materials can be used on projects that include both new construction and rehabilitation. CCPR is intended to be used as a replacement of bound and unbound materials within a new or existing flexible or composite pavement system. CCPR is typically applied at a 3 to 6 inch lifts; multiple lifts can be placed for depths exceeding 6 inches. A layer coefficient value of 0.35 for CCPR shall be used for design purposes.

The use of CCPR materials can be assessed during the design phase or through the Value Engineering process outlined in the Road and Bridge Specifications Section 104.02 (b). For design purposes, the designer may choose to exclusively use CCPR materials or select a dual design option. In the latter case, the department will advertise the project with two different sets of pavement structure (conventional and with CCPR materials) and two different sets of pay items/estimated quantities.

The designer (or the contractor while submitting Value Engineering proposal) must ensure that the alternative pavement design Structural Number (SN) of the CCPR alternative used shall meet or exceed the total Structural Number of the original design.

In addition the CCPR materials can be used as 1:1 replacement for conventional asphalt materials for the following low risk situations.

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January 2018

• Shoulder Construction – For shoulders that do not serve as a restricted travel lane, the ratio may be reduced to 1:1 and a single lift of asphalt material (i.e. asphalt concrete, slurry seal, surface treatment) will be placed over the finished CCPR.

• Trench Widening –CCPR materials can substitute IM-19.0T and BM-25.0T for Type I Trench Widening at a 1:1 ratio.

(e) Surface Layer Options

Typically, cold pavement recycling projects are surfaced by one or more layers of asphalt concrete. The thickness is usually determined by structural capacity requirements (refer to Manual of Instructions, Section 600). However, cold pavement recycled materials can be surface treated on low volume routes.

However, for all Interstate routes, the cold pavement recycled materials shall be covered with a multi-layer asphalt concrete overlay having a minimum combined thickness of 4.0 inches. For routes other than Interstates where the design traffic exceeds two way AADTT of 200, the cold pavement recycled materials shall be covered with a multi-layer asphalt concrete overlay having a minimum combined thickness of 4.0 inches. Asphalt concrete leveling courses are not to be considered as part of the multi-layer asphalt concrete overlay.

(f) Final Project Selection

After completion of the project level forensic investigation and identifying the failure mechanism, the final treatment selection shall be made by assessing all the competing options with estimated cost, time, and any other project specific constraints. Project specific constraints to consider include pavement grade. CIR and FDR material can increase 10 to 15% in volume compared to the original in-place materials. This additional volume of recycled layer should be accounted for in the final elevation. If the final depth of recycled layer and asphalt overlay is not acceptable, consideration of pre-milling the existing pavement or profile milling should be given. In cases where trench widening is part of the project, impacts to the grade may be minimized but should still be reviewed as previously stated. Depending on the project specific conditions, pavement recycling may or may not be selected. If applied appropriately, pavement recycling is expected to reduce project cost and/or completion time.

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Projects where more than 4 inches of milling is deemed necessary to remove deteriorated materials, recycling shall be considered as a solution. If recycling is not the best solution for the project, justification must be included in the design recommendations. A pavement evaluation report for the recycling projects can be sent to Pavement Design and Evaluation section of CO Materials for review at the discretion of the District Materials Engineer; however, completed copies of all pavement evaluation reports for recycling projects are to be sent to CO Materials for information.

SEC. 608.04 EXCEPTIONS

Any exceptions to these Guidelines will be documented in the final pavement report.

VI-90

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